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0032-0935
1432-2048
Springer Berlin Heidelberg Berlin/Heidelberg

39256219
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10.1007/s00425-024-04508-w
Original Article
Responses of leaf gas exchange and metabolites to drought stress in different organs of sugarcane and its closely related species Erianthus arundinaceus
http://orcid.org/0000-0002-6238-1078
Takaragawa Hiroo htakaragawa@affrc.go.jp
takaragawah0318@jircas.go.jp

1
http://orcid.org/0000-0002-3556-2404
Wakayama Masataka 23
1 https://ror.org/005pdtr14 grid.452611.5 0000 0001 2107 8171 Tropical Agriculture Research Front, Japan International Research Center for Agricultural Sciences, Maezato Kawarabaru, Ishigaki, Okinawa 907-0002 Japan
2 https://ror.org/017hkng22 grid.255464.4 0000 0001 1011 3808 Integrated Medical and Agricultural School for Public Health, Ehime University, Tōon, Ehime 791-0295 Japan
3 https://ror.org/02kn6nx58 grid.26091.3c 0000 0004 1936 9959 Institute for Advanced Biosciences, Keio University, Tsuruoka, Yamagata 997-0052 Japan
Communicated by Dorothea Bartels.

10 9 2024
10 9 2024
2024
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9 8 2024
© The Author(s) 2024
2024
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Main conclusion

The high intrinsic water-use efficiency of Erianthus may be due to the low abaxial stomatal density and the accumulation of leaf metabolites such as betaine and gamma-aminobutyric acid.

Abstract

Sugarcane is an important crop that is widely cultivated in tropical and subtropical regions of the world. Because drought is among the main impediments limiting sugarcane production in these regions, breeding of drought-tolerant sugarcane varieties is important for sustainable production. Erianthus arundinaceus, a species closely related to sugarcane, exhibits high intrinsic water-use efficiency (iWUE), the underlying mechanisms for which remain unknown. To improve the genetic base for conferring drought tolerance in sugarcane, in the present study, we performed a comprehensive comparative analysis of leaf gas exchange and metabolites in different organs of sugarcane and Erianthus under wet and dry soil-moisture conditions. Erianthus exhibited lower stomatal conductance under both conditions, which resulted in a higher iWUE than in sugarcane. Organ-specific metabolites showed gradations between continuous parts and organs, suggesting linkages between them. Cluster analysis of organ-specific metabolites revealed the effects of the species and treatments in the leaves. Principal component analysis of leaf metabolites confirmed a rough ordering of the factors affecting their accumulations. Compared to sugarcane leaf, Erianthus leaf accumulated more raffinose, betaine, glutamine, gamma-aminobutyric acid, and S-adenosylmethionine, which function as osmolytes and stress-response compounds, under both the conditions. Our extensive analyses reveal that the high iWUE of Erianthus may be due to the specific accumulation of such metabolites in the leaves, in addition to the low stomatal density on the abaxial side of leaves. The identification of drought-tolerance traits of Erianthus will benefit the generation of sugarcane varieties capable of withstanding drought stress.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s00425-024-04508-w.

Keywords

Metabolome
Photosynthetic rate
Stomatal conductance
Stomatal density
Transpiration efficiency
Water use efficiency
Whole-plant metabolomics
http://dx.doi.org/10.13039/501100009472 Japan International Research Center for Agricultural Sciences issue-copyright-statement© Springer-Verlag GmbH Germany, part of Springer Nature 2024
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pmcIntroduction

Sugarcane (Saccharum spp.) is produced on approximately 26 million hectares in more than 90 tropical and subtropical regions and countries (FAOSTAT 2022). It is an important crop responsible for much of the world’s sugar and bioethanol production. In many of these regions, water deficiency and drought are among the main weather events limiting sugarcane production; thus, proper water management and breeding of drought-tolerant sugarcane varieties are important research goals for sustainable production in these regions (Ferreira et al. 2017; Singels et al. 2019; Dlamini 2021). In sugarcane, drought stress not only attenuates physiological functions such as photosynthesis (Du et al. 1996; Zhao et al. 2013; Dinh et al. 2017; Marchiori et al. 2017) but it also significantly reduces biomass production and the final yield (Robertson et al. 1999; Basnayake et al. 2012). Therefore, improving the crop production capacity per amount of water resource applied to the field or used by the plant, namely the water-use efficiency (WUE), is important for the yield and profitability of sugarcane production, not only under rainfed conditions but also under irrigated conditions (Basnayake et al. 2012; Natarajan et al. 2020). Introducing new varieties via drought-tolerant breeding is the most effective strategy for this purpose. However, drought-tolerant varieties that have been produced are accidental products resulting from conventional selection trials in drought-prone regions and cropping seasons; efficient breeding and selection has not been conducted (Acreche 2017).

In sugarcane, the limitations of crossbreeding between varieties have been highlighted for many years, warranting the need to expand the genetic base using closely related genetic resources and to introduce their promising traits in sugarcane (Wei and Jackson 2016; Jackson 2019). In particular, Erianthus arundinaceus, a species closely related to sugarcane, is considered a genetic resource that can contribute to the improvement of drought tolerance in sugarcane through intergeneric hybridization (Jackson and Henry 2011). However, the physiological determinants of drought tolerance in Erianthus have not been thoroughly compared with those in sugarcane (Jackson and Henry 2011), and no progress has been made in searching for promising traits as selection indicators or in improving the efficiency of drought-tolerance breeding. Understanding the physiological mechanisms, as well as other important traits, is important for efficient drought-tolerance breeding in sugarcane (Jackson et al. 1996).

In crops that are large and cultivated for long periods of time, such as sugarcane, WUE is considerably impacted by environmental factors, and its determinants are complex (Basnayake et al. 2012; Liu et al. 2016; Natarajan et al. 2020). Therefore, the physiological mechanism of WUE is commonly studied by scaling it down along both the time/phenology and size axes. Intrinsic WUE (iWUE), also known as transpiration efficiency, which is the individual leaf photosynthetic rate (An) divided by its transpiration indicator, namely stomatal conductance (gs), is recognized as the minimum unit of WUE and has been proposed as an important target in crop breeding (Condon et al. 2004).iWUE=AssimilationrateAn/Stomatalconductance(gs).

A joint research group comprising scientists from Australia and China investigated WUE in sugarcane based on individual leaf gas exchange characteristics under various soil-moisture conditions in diverse genotypes, including wild germplasm (Jackson et al. 2016; Li et al. 2017; Zhao et al. 2017; Natarajan et al. 2021). This group noted variations in iWUE among the genetic resources and suggested iWUE as a promising trait that could be correlated with WUE. Erianthus, which had a high iWUE, showed high potential as a promising genetic resource. It is, however, unclear as to which physiological factors contribute to a high iWUE. Other physiological functional traits, such as leaf morphology and metabolite concentration, should be considered as targets for physiological understanding of high iWUE and in the search for efficient selection indices.

In recent years, with the development of various analytical techniques, increasing attempts have been made to comprehensively understand the physiological and genetic functions of plants through “omics” analysis (Hong et al. 2016; Ali et al. 2019; Singh et al. 2021). Metabolomics is the comprehensive analysis of metabolites and is considered a method of phenotypic analysis that most closely reflects genomic information (Watt et al. 2010; Horgan and Kenny 2011). In addition, these techniques have potential applications in growth and disease diagnostics and in the identification of selection markers (i.e., biomarkers) of stress tolerance for use in breeding (Kumar et al. 2017; Villate et al. 2021). As of date, in sugarcane, “targeted or selective” analyses of sugars and inorganic ions in the juice (e.g., Watanabe et al. 2016) and C4 photosynthesis-related metabolites in the leaf blades (e.g., Du et al. 1996) have been performed. In recent years, metabolomics has been attempted for a “comprehensive” analysis of a wide range of metabolites (sugars, amino acids, organic acids, etc.) to investigate the mechanisms of sugar accumulation in stems (Glassop et al. 2007; Perlo et al. 2022), and to identify functional components in leaf blades and cane juice (Coutinho et al. 2016; Date et al. 2022) and biomarkers for breeding and selection (Kumar et al. 2017; Villate et al. 2021). However, metabolomics studies in sugarcane have been scarce compared with those in other crops (Langridge and Fleury 2011). Although metabolomic analyses related to drought tolerance in sugarcane were performed in a few studies, investigations have been limited to comparisons among varieties (Vital et al. 2017; Budzinski et al. 2019). No metabolome analysis has focused on interspecific differences in iWUE of sugarcane and closely related genetic resources (e.g., Erianthus).

As with many other crops, studies on the effects of soil drought on sugarcane metabolites have mainly focused on the youngest fully expanded leaf (Du et al. 1996; Budzinski et al. 2019), which is the most active site for gas exchange, and other individual organs and leaf ages have not been considered. Gas exchange rates at different leaf ages were determined in a few studies (Meinzer and Grantz 1989; Marchiori et al. 2014). The existence of a stress-sensitive gradation of organs from roots to the aboveground tip of plants exposed to drought conditions has been suggested, based on the corresponding variations in metabolites (some osmolytes, such as proline) and water potential among some organs (Westgate and Boyer 1985; Choluj et al. 2008; De Souza et al. 2015; Adnan et al. 2021; Sapes and Sala 2021). In addition, metabolites that accumulate in leaves, which are the sites of gas exchange, are not necessarily biosynthesized in leaves. To understand the stress-response mechanisms of plants, it is necessary to determine the trends in the accumulation of metabolites and understand the relationship among them. However, whole-plant metabolomic analysis to identify the organs/parts most responsive to soil drying and the metabolites associated with iWUE has never been attempted in sugarcane and related germplasm. We surmised that a comprehensive analysis of metabolites accumulated at various sites in Erianthus, a promising genetic resource for drought-tolerance breeding, would facilitate a better understanding of drought tolerance and iWUE physiology in sugarcane. The present study was conducted to investigate the responses of leaf gas exchange characteristics and primary metabolites in various parts of sugarcane and Erianthus under wet and dry soil conditions, with the aim of identifying useful traits related to drought tolerance.

Materials and methods

Plant materials

A pot trial was performed in a temperature- and humidity-controlled glasshouse (Day/night temperature at 30/27 °C, relative humidity 70%) at the Tropical Agriculture Research Front, Japan International Research Center for Agricultural Sciences (24°22′43′′ N, 124°11′4′′ E). Natural radiation was introduced in the glasshouse without supplemental lighting. The average of daily accumulated solar radiation in the greenhouse during the experiment was 12.4 ± 5.1 mol m−2 day−1. Sunrise and sunset times during the experiment were 6:20 am/7:13 pm on Aug. 20 and 6:39 am/6:20 pm on Oct. 10. Sugarcane variety ‘NiF8’ and Erianthus arundinaceus accession ‘JW630’ were used for the analyses. One-node seedlings of Erianthus (May 14, 2021) and sugarcane (June 2, 2021) were planted in 518 mL volumetric polyethylene pots (10.5 cm top diameter × 7.0 cm bottom diameter × 8.5 cm height) filled with potting soil mix (pH, 5.6; electrical conductivity, 527 µS cm−1) to start seedling growth. Because germination of Erianthus was slow in the preliminary test, we started raising Erianthus seedlings half a month earlier for aligning the growth stages with those of sugarcane. When two to three leaves were fully developed (July 19, 2021), the seedlings were transplanted to 1/2000a Wagner pots (25.6 cm top diameter × 23.4 cm bottom diameter × 29.7 cm height) filled with 10 kg of the same soil, with four replicates per treatment. A soil-moisture sensor (EC-5, METER Group, Inc., Pulman, WA, USA) was inserted at a soil depth of 15 cm, and data were recorded at 15-min intervals using a data logger (ZL6, METER). Solid fertilizer (N:P:K = 2.4:0.7:1.0 g pot−1) was applied at transplantation. Until the start of the irrigation treatment, the plants were irrigated using automatic drip irrigation three times a day. With a sufficient amount of water to avoid drought stress, the water was allowed to drain freely from the bottom of the pots. The irrigation treatment was initiated 43 days after transplanting (August 30) by plugging the bottom of the pot. According to Dinh et al. (2017), wet treatment was performed by manually adding the daily consuming amount of water, while dry treatment was performed by gradually reducing the volume water content (VWC) 1% daily, depending on weather conditions for approximately 3 weeks. Finally, the plants were exposed to intense drought stress (pF > 4.0) for approximately another 3 weeks. Water consumption was estimated on the basis of soil-moisture sensor observations, soil volume, and soil bulk density.

Leaf gas exchange measurements

The gas exchange characteristics were determined at the middle part of leaves for each leaf age—the upper (youngest fully developed leaf), middle (third leaf), and lower (fifth leaf) leaves (Fig. 1)—using a portable gas exchange measuring device (LI-6400, LI-COR BioSciences, Lincoln, NE, USA) from 10 am to 2 pm for 3 days (October 7 to October 9, 2021) before harvesting. Measurements were performed with four plants under the following conditions: high light (2000 µmol m−2 s−1) and low-light (500 µmol m−2 s−1) intensity provided using an LED light source (6400-02B, LI-COR), a flow rate of 400 µmol s−1, and a reference CO2 concentration of 400 µmol mol−1. The leaf temperature was maintained at 31.1 ± 1.1 °C by controlling block temperatures attached to the chamber. Vapor pressure deficit was controlled at 2.0 ± 0.3 kPa using Drierite® (W. A. Hammond Drierite Co., Xenia, OH, USA).Fig. 1 Outline of examined plant organs in the present study. Gas exchange measurements were conducted only for middle part of each leaf (blue rectangles). Each leaf tip, middle, and base was collected for metabolomics (red and blue rectangles). The upper, middle, and lower leaves indicate the first (youngest), third, and fifth fully expanded leaves, respectively. Nodes were sampled between dewlaps of first and second youngest leaves (upper node), third and fourth leaves (middle node), and fifth and six leaves (middle node). Each node contained stem, outer and inner leaf sheaths. In Erianthus, the upper and middle nodes contained undeveloped tissues rather than stem. Only the main stem was sampled. The total number of parts sampled per plant was 19 (leaf: 9; stem: 3; leaf sheath: 6; root: 1)

Visualization of leaf anatomy

Stomatal replicas of the adaxial and abaxial surfaces of the leaves used for gas exchange measurements (n = 4) were collected according to Wu and Thao (2017). A nail polish was brushed on the leaf surface. After it dried, the thin layer of nail polish was collected using double-sided tape. The sample of stomatal replica on a glass slide was observed by light microscopy. Transverse cross-sections (approximately 40 µm thick) of the tested leaves were prepared manually using a hand microtome (THK, Kenis Ltd., Osaka, Japan). Stomatal replicas and cross-sections were observed under an optical microscope (Eclipse E800, Nikon, Tokyo, Japan) and the stomatal density and interveinal distance were evaluated using an image analysis software (NIS-elements, Nikon) (Fig. S1).

Metabolome analysis

Sample preparation

Based on the results of gas exchange measurements, one moderate-grown individual plant was selected. At 85 days after transplanting (42 days after the start of treatment), the plant was harvested for metabolome analysis. Total fresh leaf numbers were 6 under dry condition and 10 under wet condition for sugarcane, while 7 under dry condition and 8 under wet condition for Erianthus. Individual sample variations could lead to potential erroneous data interpretation under big data analysis of numerous metabolite concentrations. Because variations among individuals might be widely influenced by external factors such as growth conditions, time of sampling, and weather on the day of sampling, a single individual plant was examined. The plantlets were immediately separated into upper leaves and upper nodes, middle leaves and middle nodes, lower leaves and lower nodes, and roots (Fig. 1). Nodes were sampled between dewlaps (conjunction between leaf and leaf sheath) of first and second youngest leaves (upper node), third and fourth leaves (middle node), and fifth and six leaves (middle node). Leaves were separated into tip, middle, and basal parts, and nodes were separated into outer and inner leaf sheaths, and stem (a total of 19 parts for each plantlet). The roots were thoroughly washed and a part of it was collected. Although Erianthus vigorously produced tillers, only the main stem was targeted. For the upper and middle nodes of Erianthus, undeveloped tissues, excluding the external and internal leaf sheaths, were sampled because no clear stem was observed. Each part was packed in a labeled non-woven fabric bag (TOPVALU Dashi Pack, 12.0 cm × 9.5 cm), frozen in liquid nitrogen to stop enzymatic activity, and stored frozen at − 80 °C. For temperature-stabilized analysis, completely frozen materials were freeze-dried in a freeze-dryer (freeze trap: VA-800R, Taitec Corp., Saitama, Japan; vacuum pump: GLD-137CC, Ulvac., Kanagawa, Japan) in a cooling trap at − 70 °C for 7 days until the sample was depressurized below 10 Pa (Kim and Verpoorte 2010; Hamid et al. 2018). The frozen dry matter weight was measured for calculating the dry matter percentage, and the samples were vacuum-packed and frozen until analysis. Freeze-dried samples were placed in a 50 mL crush tube (ST-5010PCR, Yasui Kikai, Co., Osaka, Japan) with a special metal cone (MC-5012R, Yasui Kikai, Co., Osaka, Japan), precooled in liquid nitrogen, and ground using a crusher (Multi-Beads Shocker® MB-3000, Yasui Kikai, Co.) at a rotational speed of 2500 rpm for 30 s in two sets.

Sample extraction

Five mg of freeze-dried sample powder was weighed into a 2 mL microtube. To it, 400 µL of MeOH containing 200 µM internal standard solution [l-methionine sulfone, d-camphor-10-sulfonic acid (CSA), 13C6-glucose, 2-(N-morpholino) ethane sulfonic acid (MES)] was added, and the mixture was stirred (2500 rpm, 3 min) and centrifuged (9100 g, 5 min). Milli-Q water (400 µL) was added to the mixture, and the mixture was stirred again (2500 rpm, 3 min) and centrifuged (4 °C, 9100 g, 10 min) using a cooling centrifuge (MX-307, Tomy Seiko Co., Ltd., Tokyo, Japan). The supernatant (400 µL) was filtered through an ultrafiltration filter (MW 5000 kDa, HMT, Inc., Tsuruoka, Japan) using a cooling centrifugation (4 °C, 9100 g, 3 h). The filtrate was dispensed into 30 µL aliquots for liquid chromatography-mass spectrometry (LC–MS). For capillary electrophoresis-mass spectrometry (CE-MS), 100 µL filtrate was dried using a vacuum centrifuge (CentriVap Concentrator, Labconco Corp., Kansas City, MO, USA) at 4 °C for 4 h. The dried sample was diluted with 20 µL of Milli-Q water containing 200 µM of internal standard for analytical time correction for CE-MS.

Conditions for free sugar analysis using liquid chromatography-tandem mass spectrometry (LC–MS/MS)

LC–MS/MS analysis of the extracted samples was performed using an API 3000 Quadrupole LC/MS/MS tandem mass spectrophotometer system (Sciex, Framingham, MA, USA) equipped with an Agilent 1100 series column oven (Agilent Technologies, Santa Clara, CA, USA), an LC binary pump, and an autosampler (Hamid et al. 2018, 2019; Ogura et al. 2020). The extract (0.3 µL) was analyzed using a hydrophilic interaction chromatography (HILIC) amino column (Asahipak NH2P-50E; 4.6 mm inner diameter (i.d.) × 250 mm length; 5 µm; Showa Denko K.K., Tokyo, Japan) and detected using multiple reaction monitoring in the negative ion mode (Hamid et al. 2019). Cationic metabolites, including amino acids, were analyzed using forward electrophoresis (1 M formic acid) on fused silica capillaries in the positive-ion mode. Anionic metabolites, including sugar phosphates and organic acids, were analyzed using reverse directional electrophoresis (50 mM aqueous acetate-ammonium solution, pH 8.5) on coated capillaries with suppressed electroosmotic flow. Quantification by molecular weight was performed by mass spectrometry using an Agilent capillary electrophoresis system consisting of an Agilent G6220A LC/MSD TOF, an Agilent 1100 series isocratic HPLC pump, a G1603A Agilent CE-MS Adapter Kit, and a G1607A Agilent CE-ESI–MS Sprayer Kit (Agilent Technologies) in full scan mode from m/z 50–1000 (Wakayama et al. 2015). Standard mixtures were prepared and measured for each analysis to identify the peak of each metabolite in the sample solution and to quantify the amount of each metabolite. Finally, the metabolite concentration per dry matter weight was calculated and used for various analyses including multivariate analysis.

Statistical analysis

Multivariate analysis of all metabolite data was performed using principal component analysis (PCA) and hierarchical clustering analysis (HCA) with JMP ver. 17.0.0 (SAS Institute Inc., Cary, NC, USA), as described previously (Hamid et al. 2020; Ogura et al. 2020). HCA was performed using the Ward’s method for two-way clustering of metabolite concentrations and analyzed samples. To elucidate any trend in concentration of metabolites, PCA was performed on all samples and leaf blades only.

To determine the significant differences in the concentration of each metabolite between genotypes and treatments, P values between genotypes and treatments for each metabolite were calculated and volcano plots were created for each organ or part, except the root, for each case.

Analysis of variance (ANOVA) was performed to determine the effects of genotype, water regime, and leaf age (1st, 3rd, and 5th; Fig. 1), and their interactions. Differences in the mean values of leaf gas exchange, anatomical features (n = 4), and concentrations of targeted metabolites between the genotypes or water regimes were determined using the t-test (n = 3). Differences in the mean values for the analyzed leaf ages (1st, 3rd, and 5th) or leaf parts (tip, middle, and base; Fig. 1) between the genotypes or water regimes were determined using the Tukey’s test (P < 0.05). These analyses and tests were performed using the statistical analysis software (Bell Curve for Excel; Social Survey Research Information Co., Ltd., Tokyo, Japan).

Results

Leaf gas exchange and anatomical characteristics in response to drought stress

The trends of soil moisture are shown in Fig. 2. The average VWC in the wet treatments was 34.5 ± 4.6% for the two species (Fig. 2, yellow and blue lines). In the dry treatments, the VWC reached ~ 10% in approximately 4 weeks after the start of the soil drying treatment, and the drought stress was continued for approximately 3 weeks until the end of the experiment (Fig. 2, red and green lines). The average VWC in the dry treatment from September 24 to October 12 was 10.6 ± 1.7% for the two species.Fig. 2 Changes of soil volume water content (VWC) during the experiment. Soil water treatment was started at 43 days after transplanting based on VWC readings (black arrow). Number of x axis in parenthesis indicates days after transplanting. VWC for sugarcane pot under dry and wet conditions was indicated by red and orange lines, respectively. VWC for Erianthus pot under dry and wet conditions was indicated by green and blue lines, respectively

The leaf gas-exchange characteristics for each leaf age are listed in Table 1. ANOVA based on the means and significance of differences between genotypes, treatments, and leaf ages are also shown in Tables S1 and S2. Photosynthetic rate (A) and stomatal conductance (gs) were lower in the lower leaves than in the upper and middle leaves. This trend was particularly apparent for sugarcane in the wet treatment and for Erianthus in the dry treatment. A tended to be lower in Erianthus than in sugarcane as a whole. gs of Erianthus was significantly lower than that of sugarcane, regardless of the light conditions, except for the lower leaves in the wet treatment and for the upper leaves in the dry treatment. iWUE was significantly higher in Erianthus than in sugarcane, except for the lower leaves in the wet treatment. Such genotypic differences in gs and iWUE were more remarkable under low-light conditions than under high-light conditions regardless of soil water conditions. Table 1 Gas exchange parameters measured under different water regime and light intensity conditions

Water regime	PPFD (µmol m−2 s−1)	Genotype	A (µmol m−2 s−1)	gs (mol m−2 s−1)	iWUE (µmol mol−1)	
Upper	Middle	Lower	Upper	Middle	Lower	Upper	Middle	Lower	
Wet	Unsaturated (500)	Sugarcane	21.0	20.3	18.0	0.28	0.30	0.17	75.5	69.4	104.8	
Erianthus	17.9	16.9	16.0	0.14	0.15	0.14	129.3	118.1	119.7	
Saturated (2000)	Sugarcane	35.5	34.8	29.2	0.31	0.35	0.23	113.3	101.6	124.6	
Erianthus	30.3	28.0	25.2	0.23	0.23	0.21	131.9	120.6	119.4	
Dry	Unsaturated (500)	Sugarcane	17.2	18.2	16.7	0.13	0.14	0.14	130.3	133.9	124.4	
Erianthus	15.2	15.1	12.7	0.09	0.08	0.07	179.4	185.5	178.6	
Saturated (2000)	Sugarcane	27.3	29.6	25.2	0.19	0.22	0.18	144.9	137.8	139.5	
Erianthus	24.9	22.6	17.3	0.15	0.13	0.10	163.5	174.0	178.0	
PPFD, A, gs, and iWUE refer to photosynthetic photon flux density, photosynthetic rate, stomatal conductance, and intrinsic water-use efficiency, respectively. The results of the statistical analyses are presented in Tables S1 and S2

Stomatal density and interveinal distance were measured in the sugarcane and Erianthus leaves. No significant difference in stomatal density on the adaxial leaf surface was noted between Erianthus and sugarcane but Erianthus had significantly lower stomatal density on the abaxial leaf surface (Tables 2 and S2). Therefore, the total stomatal density in Erianthus was significantly lower, except in the upper leaves in the dry treatment, and the ratio of stomatal distribution on the adaxial and abaxial surfaces was significantly higher. The interveinal distance was significantly greater in the Erianthus. ANOVA showed that the abaxial stomatal density and stomatal-distribution ratio were less affected by leaf age and treatment and were characteristic for the two species (Tables S1 and S2). Table 2 Stomatal density and interveinal distance

Water regime	Genotype	Stomatal density (no. mm−2)	Adaxial / abaxial ratio	Interveinal distance (µm)	
Adaxial	Abaxial	Total	
Upper	Middle	Lower	Upper	Middle	Lower	Upper	Middle	Lower	Upper	Middle	Lower	Upper	Middle	Lower	
Wet	Sugarcane	96.8	88.4	85.2	181.7	167.6	171.4	278.5	256.1	256.6	0.53	0.53	0.50	122.7	126.7	123.8	
Erianthus	91.9	91.0	88.5	131.5	128.1	124.8	223.5	219.1	213.3	0.70	0.71	0.71	139.7	141.8	140.5	
Dry	Sugarcane	93.5	94.8	90.1	171.6	172.1	183.3	265.0	267.0	273.4	0.55	0.55	0.49	128.8	130.8	122.8	
Erianthus	103.2	96.5	88.7	144.2	133.8	125.3	247.3	230.3	214.1	0.72	0.72	0.71	147.0	149.1	151.7	
Results of statistical analysis are presented in Tables S1 and S2

Profiling of plant metabolites in response to drought stress using multivariate analysis

A total of 188 metabolites were detected and quantified. Hierarchical clustering analysis (HCA) was performed using the concentration of each metabolite as an explanatory variable (Fig. 3). The organs were broadly classified from source-capable leaf parts (tip and middle parts of leaf in the two genotypes and base part of sugarcane leaf) to sink organs (base part of the Erianthus leaf, leaf sheath, and stem/root of both genotypes). The basal part of the Erianthus leaf was classified as a sink organ, not a source organ, because the dewlap (conjunction between leaf and leaf sheath) was indistinct, and the basal part of leaf showed a morphology similar to that of the leaf sheath. Furthermore, there was a tendency for clustering according to the genotype and adjacent parts from the leaf blade to the leaf sheath. For each cluster of leaf parts, the effect of the treatments (dry and wet) was moderate within each cluster (Fig. 3, arrows).Fig. 3 Hierarchical clustering analysis (HCA) and heatmap of dry weight-based metabolite concentrations after freeze-drying. All quantified concentrations were normalized to Z-scores for metabolite concentration. Blue and red indicate low and high concentrations, respectively. The legends for the plant parts are shown in. Color-changing arrows indicate soil water conditions (dry: yellow; wet: blue)

PCA was performed using the metabolite concentrations in all plant parts as explanatory variables. Despite the integration analysis of the two genotypes, principal component (PC) 1 (32% contribution) showed a difference between the stem and other organs, whereas PC2 (15.3%) showed a difference between the leaves and other organs. The difference between the two genotypes was confirmed as PC3 (6.74%). Although PC1–PC5 were analyzed, the effects of the treatment were not detected.

To determine the effects of genotypes and treatments, PCA was performed using only the metabolite data for the leaves (Fig. 4), in which these effects were evident in the cluster analysis (Fig. 3). PC1 (24.6% contribution) showed a difference between the two genotypes, PC2 (14.6%) showed a difference between the leaf parts, and PC3 (8.63%) showed the effect of the treatment (Fig. 4). In contrast, the effect of leaf age was weak in PC5 (6.29%). Therefore, a loading plot of PC1, which represented the difference between the two genotypes, and PC3, which represented the effect of the treatments, allowed us to capture the metabolites that specifically accumulated in each genotype under each soil-moisture condition (Fig. 5). This type of loading plot was used to qualitatively analyze the concentrations of metabolites. For example, in the negative region of PC1, which indicates that the metabolite concentration is likely to be high in Erianthus, we found metabolites, such as betaine, GABA, glutamine, proline, and raffinose, whereas in the positive region of PC1, which indicates that the metabolite concentration is likely to be higher in sugarcane, we found metabolites, such as isocitrate, pyruvate, glutamate, mannitol, spermine, and putrescine. In the positive region of PC3, which indicates high concentration under dry conditions, sugars and polyols (sucrose, glucose, and raffinose), amino acids (tyrosine and tryptophan), and polyamines were found.Fig. 4 Principal component analysis (PCA) score plots for leaf parts. The metabolite concentrations used for the PCA were calculated based on the dry weight after freeze-drying. Percentage in parentheses indicates the contribution ratio of each principal component. The PCA loading scores are presented in Table S4

Fig. 5 Principal component analysis (PCA) loading plots for leaf parts. The metabolite concentrations used for the PCA were calculated based on the dry weight after freeze-drying. Percentage in parentheses indicates the contribution ratio of each principal component. The PCA loading scores are listed in. Red, blue, green, and pink symbols indicate selected polyols and saccharides, amino acids, organic acids, and nitrogen-related metabolites other than amino acids, respectively

Changes in metabolite concentrations in different organs and parts under different water conditions

The metabolites were classified into different chemical component groups, and the concentrations and compositions in the plant organs and parts are shown using stacked graphs (Fig. 6). The stacking graph for the accumulated concentrations shows that polyols/sugars and amino acids were markedly affected by soil drying, regardless of the genotype (Fig. 6a, c). In contrast, N metabolites other than amino acids showed little change in concentrations with soil drying, and only the concentration of betaine in Erianthus tended to increase with soil drying (Fig. 6e). The concentrations of organic acids decreased slightly in the sugarcane stalks after soil drying; however, the effect of drying was generally small in both species (Fig. 6g). It is clear from part-specific data that each component group accumulated more in the stem than in the other sites (Fig. 6a, c, e, g). To determine the metabolite composition of each plant part, the metabolite gradient between adjacent parts from the root to the leaf tip was determined (Fig. 6b, d, f, h).Fig. 6 Profiling of selected metabolites in continuous whole plant parts under different water regimes. Metabolite concentrations were calculated based on the dry weight after freeze-drying. a, c, e, g Metabolite concentrations of polyols and saccharides, amino acids, other N-related metabolites, and organic acids. b, d, f, h Composition ratios of polyols and saccharides, amino acids, other N-related metabolites, and organic acids

Regarding the polyol/sugar composition, the percentages of fructose in sugarcane and glucose in Erianthus were particularly high under dry conditions (Fig. 6b). Genotypic differences in amino acid composition were small, with a high composition of glutamate and alanine in the leaves, and a high composition of aspartate and asparagine in the leaf sheath, which decreased toward the stem and roots (Fig. 6d). N metabolites, other than amino acids, were distinctly genotype-specific, with higher proportions of choline and polyamines in sugarcane, and betaine and GABA in Erianthus (Fig. 6f). Remarkable genotypic differences in the composition of organic acids were observed in the leaves, with a higher proportion of isocitrate in sugarcane, and higher proportions of malate, shikimate, and quinate in Erianthus (Fig. 6h).

To identify the components that showed significant differences between genotypes or treatments, volcano plots were prepared for each plant part other than the root, plotting P values for each metabolite for genotypic and treatment differences. The number of metabolites with significant differences (P < 0.01) between the species and between the treatments tended to be higher for the leaves and lower in the parts that were closer to the stem. Metabolites with significant differences in concentrations between treatments tended to be fewer in each plant part than those with significant differences between genotypes. The concentrations of betaine and GABA tended to be higher in Erianthus in many parts, especially in the leaves, whereas isocitrate concentration was markedly higher in sugarcane leaves. The differences between treatments showed a tendency for raffinose to increase consistently with drying.

For precise identification of the metabolites associated with stress response, we displayed the changes in the concentration of 28 metabolites, selected based on the PCA factor loadings for the leaf, in the plant parts (Fig. 5). Methionine, glutamine, GABA, betaine, and S-adenosylmethionine (SAM) accumulated more in Erianthus leaves than in sugarcane leaves under both dry and wet conditions, whereas their accumulated in the sugarcane stem was higher than in other plant parts (Fig. 7). In contrast, the accumulation of raffinose was less in sugarcane in leaves or stems, regardless of the part. GABA showed contrasting part-specific gradients between the genotypes, with sugarcane showing higher concentrations near the root, and Erianthus showing higher concentrations near the root and leaf tips.Fig. 7 Selected metabolite concentrations in leaf parts under different water regimes. Metabolite concentrations were calculated based on the dry weight after freeze-drying. Significant difference was analyzed using the mean concentrations of the three leaf ages

Changes in specific leaf metabolites in response to drought stress

As mentioned above, the effect of leaf position on metabolite variation was low, as determined using PCA. Therefore, the concentrations of the 28 metabolites mentioned above was averaged without considering the leaf age and examined as described below (Fig. 7). ANOVA results and the significance of differences in metabolite concentrations between the genotypes, treatments, and leaf parts are presented in Tables S5 and S6.

Analysis of genotypic differences in the accumulation of polyols and sugars revealed that sugarcane had higher concentrations of mannitol, inositol, and fructose, whereas Erianthus had higher concentrations of raffinose, glucose, and sucrose (Fig. 7). Among the amino acids, glutamate concentrations were higher in sugarcane, whereas the concentrations of alanine, glutamine, histidine, methionine, proline, tyrosine, and tryptophan were higher in Erianthus. Among the N metabolites other than amino acids, the concentrations of putrescine and spermine tended to be higher in sugarcane, whereas those of betaine, GABA, SAM, and cyclohexylamine were higher in Erianthus. Among the organic acids, C4 photosynthesis-related metabolites (citrate, isocitrate, malate, and pyruvate) were highly accumulated in the sugarcane.

Regarding differences between treatments, the concentrations of all polyols and sugars increased with soil drying (Fig. 7). In Erianthus, the concentrations of alanine, histidine, proline, tyrosine, and tryptophan increased with soil drying. In contrast, in sugarcane, the concentrations of histidine, tyrosine, and tryptophan decreased with soil drying. Accumulation of polyamines tended to increase with soil drying, particularly in Erianthus. The pyruvate concentration tended to increase with drying. Shikimate and quinate concentrations were higher in Erianthus, particularly under dry conditions. These metabolites are generated from the shikimate pathway, which biosynthesizes aromatic amino acids, followed by the biosynthesis of secondary metabolites, such as antioxidants and lignin. Among these, the concentrations of raffinose, glutamine, betaine, GABA, and SAM were particularly high in Erianthus, regardless of the dry or wet conditions. These trends were generally consistent with those in the PCA loading plot (Fig. 5).

Metabolite concentrations in different leaf parts exhibited significant part-specific differences, with the middle parts showing values that were intermediate between those for the tip and basal parts for many selected metabolites.

Discussion

Effects of leaf age and light conditions on genotypic differences in gas exchange and WUE

Erianthus maintained low gs regardless of leaf age (Table 1) and thus maintained high iWUE without being affected by differences in stomatal responses due to aging. In general, low gs is associated with low stomatal density (Franks et al. 2015; Caine et al. 2019; Pitaloka et al. 2022), and the low gs of Erianthus in the present study was consistent with low stomatal density, especially on the abaxial surface, and high stomatal-distribution ratio (adaxial/abaxial) (Table 2). High photosynthetic activity, even at low gs (i.e., high iWUE), may involve metabolites, such as photosynthetic enzymes and osmolytes involved in maintaining the water potential (see discussion below).

The differences in iWUE between the two genotypes were greater under low-light than under high-light conditions. In general, under low-light conditions, photosynthetic capacity is reduced, and iWUE decreases because of excessive transpiration (Ye et al. 2020; Ozeki et al. 2022). Although, in this study, young plants were grown under pot conditions with low self-shading, the low stomatal responsiveness of sugarcane under low-light conditions (Table 1) can significantly suppress photosynthesis in self-shading canopies grown under field conditions (Almeida et al. 2022), leading to a further decline in iWUE. Because C4 leaves with low-light acclimation have special anatomical characteristics (e.g., cell wall suberization and aggregated arrangement of related cells), which causes less bundle-sheath leakiness (von Caemmerer and Furbank 2003), it is necessary to focus more on the ultrastructural anatomical characteristics of Erianthus leaves in future research.

The results of ANOVA showed that the effect of leaf age on A and gs, but not on iWUE, was significant and there was no effect of interactions, including leaf age, especially under unsaturated-light conditions (Table S1). Therefore, when screening iWUE, it was necessary to select the first to the fifth leaf and to evaluate iWUE under unsaturated light with uniform soil-moisture conditions. This result should draw our attention to the fact that many previous studies on sugarcane iWUE have been conducted under saturated light conditions (photosynthetic photon flux density (PPFD) ≈ 2000 µmol m−2 s−1) using the youngest fully expanded leaf to achieve maximum photosynthetic rates (e.g., Jackson et al. 2016; Natarajan et al. 2021). In addition to physiological traits, such as gas-exchange rate and metabolite concentrations, leaf anatomical traits varied less with environmental and sampling conditions (Tables S1), which may be more suitable for genotypic comparison of iWUE and, consequently, for screening applications if the measurement throughput is improved.

The high iWUE-related leaf metabolites responding to drought are common in the two genotypes

Plants close their stomata in response to soil drought and stress and regulate plant water potential by accumulating osmolytes and other metabolites in response to the deteriorating plant water status (Boyer 1995; Hare et al. 1998). The responses of each parameter to soil drying are summarized in Table 3. In both genotypes, soil drying decreased A and gs and increased iWUE, stomatal density, and intervascular distance, whereas the stomatal density ratio was not changed much (Table 3). In addition, the concentrations of all the analyzed polyols and sugars were increased by soil drying for both genotypes. Polyols/sugars are known to accumulate under drought and salt stress and function as osmolytes in a wide range of species (Ozturk et al. 2021). Among amino acids, alanine is commonly increased with soil drying. Alanine is produced via glutamate and GABA in a GABA biosynthesis pathway called the GABA shunt (Miyashita and Good 2008) and its concentrations are commonly known to be increased under drought stress conditions (Rhodes et al. 1986). Among N metabolites other than amino acids, soil drying increased the concentrations of SAM, spermine, and spermidine, whereas little change was noticed for choline, GABA, and cyclohexylamine, which responded to drought and were present in similar amounts in the two species. Polyamines (spermine and spermidine) and their precursor, SAM, are stress-responsive compounds that accumulate under stress (Bouchereau et al. 1999). GABA is involved in stomatal closure (Kinnersley and Turano 2000; Hasan et al. 2021), and choline is a precursor of betaine, a stress-response compound (Sakamoto and Murata 2002), that may accumulate with or without stress to reduce the damage caused by the stress. Among the organic acids, the concentration of pyruvate increased, that of citrate decreased, and that of isocitrate changed slightly under drought; the responses were similar for the two genotypes (Table 3). Pyruvate is an important metabolic component of the C4 photosynthetic cycle as it is a source of PEP (Sage et al. 2013); its concentrations increase to enable alanine synthesis for stress adaptation (Rhodes et al. 1986). Both citrate and isocitrate are intermediate metabolites in the tricarboxylic acid cycle and osmotic stress has been reported to decrease the citrate concentrations (Dabravolski and Isayenkov 2023). Thus, we were able to classify metabolites that commonly respond to drought in sugarcane and Erianthus. Table 3 List of selected leaf metabolites affected by soil water regime in each genotype

Text in bold indicates greater concentration of the metabolites in the genotype

Responses of iWUE-related leaf metabolites to drought in Erianthus

In addition to polyols and sugars, the concentrations of amino acids, such as proline and betaine, shikimate pathway metabolites, polyamines, and N-related metabolites were increased by drought in Erianthus (Table 3). These diverse metabolites act as osmolytes and stress defense molecules (Raggi 1994; Weaver and Herrmann 1997), and their concentrations are suggested to increase in Erianthus under drought conditions, resulting in high iWUE. The metabolomics profiles of sugarcane leaves under drought stress have been compared between drought-tolerant and drought-susceptible varieties (Vital et al. 2017). Raffinose, glucose, betaine, proline, and tryptophan, which were commonly found at high concentrations in drought-tolerant varieties in a previous study and in Erianthus in this study, may be highly concentrated metabolites common to drought-tolerant genotypes. In addition, high concentrations of stress-responsive substances, such as GABA and SAM, were present in Erianthus under dry conditions, but not in sugarcane (Fig. 5). GABA is a non-protein amino acid biosynthesized from polyamines via proline and glutamate and is also implicated in plant stress responses (Kinnersley and Turano 2000; Hasan et al. 2021). In particular, its involvement in maintaining turgor pressure and low gs has been noted (Xu et al. 2021), which is consistent with the low gs in Erianthus (Table 1).

The iWUE of Erianthus was higher than that of sugarcane, even under wet conditions, except for the lower leaves (Table 1). The stomatal-distribution ratio and methionine, glutamine, and GABA concentrations exhibited minor changes upon drying, and were higher than those in sugarcane (Table 3). In addition, the concentrations of raffinose, betaine, and SAM were higher in Erianthus than in sugarcane under both dry and wet conditions, although they increased under conditions of drought (Fig. 7). Therefore, the stomatal-distribution ratio and concentrations of these six metabolites are likely involved in establishing a potentially high iWUE for Erianthus.

Responses of iWUE-related leaf metabolites to drought in sugarcane

In sugarcane leaves, osmolytes, such as mannitol, inositol, fructose, and polyamines (spermine and putrescine), as stress-response substances, glutamate as a precursor of GABA, and isocitrate as a precursor of glutamate, alanine, and pyruvate, which are used in alanine synthesis, were highly concentrated under dry conditions (Figs. 5 and 7). Proline, GABA, SAM, glutamine, polyamines, and methionine are closely involved in metabolic pathways and have been implicated in drought tolerance in plants (Ravanel et al. 1998; Silvente et al. 2012; Hasan et al. 2021). In particular, sugarcane leaves showed higher glutamate concentrations, but lower concentrations of glutamine, proline, and GABA, which are produced from glutamate, than the respective concentrations in Erianthus (Figs. 5 and 7). Moreover, polyamines are believed to be the precursors to GABA; however, the high polyamine concentration in sugarcane was not linked to increased GABA concentration in this study. This suggests that biochemical and physiologic characteristics, such as the abundance and degree of activity of polyamine dehydrogenase (polyamine oxidase) (Prabu et al. 2011) and the negative feedback between GABA and polyamine biosynthesis (Wang et al. 2014), may be related to genotypic differences in iWUE. Glutamate, alanine, and pyruvate are components of the GABA biosynthesis pathway, known as the GABA shunt (Miyashita and Good 2008; Hassan et al. 2021). Moreover, isocitrate, a metabolite in the citric acid cycle, is consumed in the synthesis of glutamate via 2-oxaglutarate (Popova and de Carvalho 1998). Because sugarcane produces large amounts of isocitrate, it was suggested that large amounts of glutamate were synthesized from the abundant isocitrate, and large amounts of alanine were synthesized from the abundant glutamate and pyruvate (Figs. 6 and 7). Sugarcane may be unique in that the abundant glutamate is consumed in alanine synthesis under abundant pyruvate conditions, and therefore, does not lead to an increase in GABA concentration.

Sugarcane accumulated less amounts of the osmolyte betaine and more of choline, which is a betaine precursor, regardless of the dry or wet condition (Figs. 6 and 7). The low activity of the catalytic enzyme choline monooxygenase, which oxidizes choline (Sakamoto and Murata 2002), was considered as the reason why the increase in choline concentrations was not linked to the increase in betaine concentrations in sugarcane. In terms of the trends in part-specific accumulation, betaine tended to accumulate more in the stem, although in smaller amounts, in sugarcane, whereas it tended to accumulate in both the stem and leaf blades in Erianthus. This difference in accumulation between sites implies a preferential target for protection against stress (Hattori et al. 2009), and suggests that in sugarcane, the priority is to maintain the moisture status in the stem.

Challenges in biomarker identification and the need for a detailed investigation of the causal relationship of metabolites with iWUE

HCA suggested that leaves were associated with interspecific differences in iWUE (Fig. 3). Furthermore, the results of the PCA for the leaf (Fig. 4) suggested that leaf sampling should be carefully performed for metabolome analysis, and that the effect of leaf age from the first to the fifth youngest leaf was small. The small effect of leaf age on metabolite concentrations was consistent with the small effect of leaf age on iWUE (Table S1), supporting the lesser need to consider the effect of leaf age, at least at the 4-month-old growth stage, when assessing iWUE-related metabolites (i.e., for creating biomarkers).

The results of this study could not completely clarify the causal relationship between the various metabolites, iWUE, and drought tolerance. Therefore, with regard to GABA, it is necessary to conduct transcriptome analysis in future and to analyze the activity of each degradative enzyme in combination with metabolomics to clarify the causal relationship between GABA biosynthesis and stress response in the two genotypes. If these specific metabolites are to be used as biomarkers for high-throughput phenotyping of WUE and drought tolerance, it is desirable to screen them in the very early growth stages when they are relatively unaffected by the environment (i.e., when the genotype effect is stronger). However, the phenotype and gene expression may vary with growth stage and time (Boyes et al. 2001), and there may be discrepancies between plants at the very early growth stage in greenhouses and mature plants established in the field (Strock et al. 2022). Regarding the effects of growth stage on metabolome sampling, it is also necessary to investigate the variation among individuals. Therefore, a more precise verification, such as expression analysis on a timescale using several replicates, is required in future. In addition, it is necessary to further investigate and analyze the population of intergeneric hybrids between sugarcane and Erianthus for quantitative trait locus analysis to create genetic markers.

Supplementary Information

Below is the link to the electronic supplementary material.Supplementary file1 (PDF 3,357 kb)

Abbreviations

A Photosynthetic rate

gs Stomatal conductance

GABA γ-Aminobutyric acid

iWUE Intrinsic water use efficiency

SAM S-adenosylmethionine

Acknowledgements

We are most grateful to Ms. Rie Kadowaki, Dr. Hiroki Onuma, Dr. Tatsuki Ogura, Ms. Narumi Adachi, and many other staffs at Tsuruoka metabolome campus of Keio university for providing great supports in chemical analysis and data processing including peak annotation.

Author contributions

HT and MW designed the study. HT cultivated the plant materials, carried out gas-exchange measurements, and plant sampling. HT and MW performed metabolome analysis, data analyses, and manuscript writing.

Funding

This research has not received any specific grant from any funding agency, public, commercial or non-profit, other than the operating grant that our affiliated institution (JIRCAS) receives from the Ministry of Agriculture, Forestry and Fisheries (MAFF).

Data availability

The data supporting the findings of this study are available from the corresponding author, (Hiroo Takaragawa), upon request.

Declarations

Conflict of interest

No conflict of interest declared.

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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References

Acreche MM Nitrogen-, water- and radiation-use efficiencies affected by sugarcane breeding in Argentina Plant Breed 2017 136 2 174 181 10.1111/pbr.12440
Acreche MM (2017) Nitrogen-, water- and radiation-use efficiencies affected by sugarcane breeding in Argentina. Plant Breed 136(2):174–181. 10.1111/pbr.1244010.1111/pbr.12440
Adnan MY Hussain T Ahmed MZ Gul B Khan MA Nielsen BL Growth regulation of Desmostachya bipinnata by organ-specific biomass, water relations, and ion allocation responses to improve salt resistance Acta Physiol Plant 2021 43 1 12 10.1007/s11738-021-03211-7
Adnan MY, Hussain T, Ahmed MZ, Gul B, Khan MA, Nielsen BL (2021) Growth regulation of Desmostachya bipinnata by organ-specific biomass, water relations, and ion allocation responses to improve salt resistance. Acta Physiol Plant 43:1–12. 10.1007/s11738-021-03211-710.1007/s11738-021-03211-7
Ali A Khan M Sharif R Mujtaba M Gao SJ Sugarcane Omics: an update on the current status of research and crop improvement Plants 2019 8 9 344 10.3390/plants8090344 31547331
Ali A, Khan M, Sharif R, Mujtaba M, Gao SJ (2019) Sugarcane Omics: an update on the current status of research and crop improvement. Plants 8(9):344. 10.3390/plants809034431547331 10.3390/plants8090344
Almeida RL Silveira NM Miranda MT Pacheco VS Cruz LP Xavier MA Machodo EC Ribeiro RV Evidence of photosynthetic acclimation to self-shading in sugarcane canopies Photosynthetica 2022 60 4 521 528 10.32615/ps.2022.045
Almeida RL, Silveira NM, Miranda MT, Pacheco VS, Cruz LP, Xavier MA, Machodo EC, Ribeiro RV (2022) Evidence of photosynthetic acclimation to self-shading in sugarcane canopies. Photosynthetica 60(4):521–528. 10.32615/ps.2022.04510.32615/ps.2022.045
Basnayake J Jackson PA Inman-Bamber NG Lakshmanan P Sugarcane for water-limited environments. Genetic variation in cane yield and sugar content in response to water stress J Exp Bot 2012 63 16 6023 6033 10.1093/jxb/ers251 22996675
Basnayake J, Jackson PA, Inman-Bamber NG, Lakshmanan P (2012) Sugarcane for water-limited environments. Genetic variation in cane yield and sugar content in response to water stress. J Exp Bot 63(16):6023–6033. 10.1093/jxb/ers25122996675 10.1093/jxb/ers251
Bouchereau A Aziz A Larher F Martin-Tanguy J Polyamines and environmental challenges: recent development Plant Sci 1999 140 2 103 125 10.1016/S0168-9452(98)00218-0
Bouchereau A, Aziz A, Larher F, Martin-Tanguy J (1999) Polyamines and environmental challenges: recent development. Plant Sci 140(2):103–125. 10.1016/S0168-9452(98)00218-010.1016/S0168-9452(98)00218-0
Boyer JS Biochemical and biophysical aspects of water deficits and the predisposition to disease Annu Rev Phytopathol 1995 33 1 251 274 10.1146/annurev.py.33.090195.001343 18999961
Boyer JS (1995) Biochemical and biophysical aspects of water deficits and the predisposition to disease. Annu Rev Phytopathol 33(1):251–274. 10.1146/annurev.py.33.090195.00134318999961 10.1146/annurev.py.33.090195.001343
Boyes DC Zayed AM Ascenzi R McCaskill AJ Hoffman NE Davis KR Gorlach J Growth stage–based phenotypic analysis of Arabidopsis: a model for high throughput functional genomics in plants Plant Cell 2001 13 7 1499 1510 10.1105/TPC.010011 11449047
Boyes DC, Zayed AM, Ascenzi R, McCaskill AJ, Hoffman NE, Davis KR, Gorlach J (2001) Growth stage–based phenotypic analysis of Arabidopsis: a model for high throughput functional genomics in plants. Plant Cell 13(7):1499–1510. 10.1105/TPC.01001111449047 10.1105/TPC.010011
Budzinski IGF de Moraes FE Cataldi TR Franceschini LM Labate CA Network analyses and data integration of proteomics and metabolomics from leaves of two contrasting varieties of sugarcane in response to drought Front Plant Sci 2019 10 1524 10.3389/fpls.2019.01524 31850025
Budzinski IGF, de Moraes FE, Cataldi TR, Franceschini LM, Labate CA (2019) Network analyses and data integration of proteomics and metabolomics from leaves of two contrasting varieties of sugarcane in response to drought. Front Plant Sci 10:1524. 10.3389/fpls.2019.0152431850025 10.3389/fpls.2019.01524
Caine RS Yin X Sloan J Harrison EL Mohammed U Fulton T Rice with reduced stomatal density conserves water and has improved drought tolerance under future climate conditions New Phytol 2019 221 1 371 384 10.1111/nph.15344 30043395
Caine RS, Yin X, Sloan J, Harrison EL, Mohammed U, Fulton T et al (2019) Rice with reduced stomatal density conserves water and has improved drought tolerance under future climate conditions. New Phytol 221(1):371–384. 10.1111/nph.1534430043395 10.1111/nph.15344
Chołuj D Karwowska R Ciszewska A Jasińska M Influence of long-term drought stress on osmolyte accumulation in sugar beet (Beta vulgaris L.) plants Acta Physiol Plant 2008 30 679 687 10.1007/s11738-008-0166-2
Chołuj D, Karwowska R, Ciszewska A, Jasińska M (2008) Influence of long-term drought stress on osmolyte accumulation in sugar beet (Beta vulgaris L.) plants. Acta Physiol Plant 30:679–687. 10.1007/s11738-008-0166-210.1007/s11738-008-0166-2
Condon AG Richards RA Rebetzke GJ Farquhar GD Breeding for high water-use efficiency J Exp Bot 2004 55 407 2447 2460 10.1093/jxb/erh277 15475373
Condon AG, Richards RA, Rebetzke GJ, Farquhar GD (2004) Breeding for high water-use efficiency. J Exp Bot 55(407):2447–2460. 10.1093/jxb/erh27715475373 10.1093/jxb/erh277
Coutinho ID Baker JM Ward JL Beale MH Creste S Cavalheiro AJ Metabolite profiling of sugarcane genotypes and identification of flavonoid glycosides and phenolic acids J Agric Food Chem 2016 64 21 4198 4206 10.1021/acs.jafc.6b01210 27152527
Coutinho ID, Baker JM, Ward JL, Beale MH, Creste S, Cavalheiro AJ (2016) Metabolite profiling of sugarcane genotypes and identification of flavonoid glycosides and phenolic acids. J Agric Food Chem 64(21):4198–4206. 10.1021/acs.jafc.6b0121027152527 10.1021/acs.jafc.6b01210
Dabravolski SA Isayenkov SV The role of the γ-aminobutyric acid (GABA) in plant salt stress tolerance Horticulturae 2023 9 2 230 10.3390/horticulturae9020230
Dabravolski SA, Isayenkov SV (2023) The role of the γ-aminobutyric acid (GABA) in plant salt stress tolerance. Horticulturae 9(2):230. 10.3390/horticulturae902023010.3390/horticulturae9020230
Date Y Ishikawa C Umeda M Tarumoto Y Okubo M Tamura Y Ono H Sugarcane metabolome compositional stability in pretreatment processes for NMR measurements Metabolites 2022 12 9 862 10.3390/metabo12090862 36144266
Date Y, Ishikawa C, Umeda M, Tarumoto Y, Okubo M, Tamura Y, Ono H (2022) Sugarcane metabolome compositional stability in pretreatment processes for NMR measurements. Metabolites 12(9):862. 10.3390/metabo1209086236144266 10.3390/metabo12090862
De Souza AP Cocuron JC Garcia AC Alonso AP Buckeridge MS Changes in whole-plant metabolism during the grain-filling stage in sorghum grown under elevated CO2 and drought Plant Physiol 2015 169 3 1755 1765 10.1104/pp.15.01054 26336093
De Souza AP, Cocuron JC, Garcia AC, Alonso AP, Buckeridge MS (2015) Changes in whole-plant metabolism during the grain-filling stage in sorghum grown under elevated CO2 and drought. Plant Physiol 169(3):1755–1765. 10.1104/pp.15.0105426336093 10.1104/pp.15.01054
Dinh TH Watanabe K Takaragawa H Nakabaru M Kawamitsu Y Photosynthetic response and nitrogen use efficiency of sugarcane under drought stress conditions with different nitrogen application levels Plant Prod Sci 2017 20 4 412 422 10.1080/1343943X.2017.1371570
Dinh TH, Watanabe K, Takaragawa H, Nakabaru M, Kawamitsu Y (2017) Photosynthetic response and nitrogen use efficiency of sugarcane under drought stress conditions with different nitrogen application levels. Plant Prod Sci 20(4):412–422. 10.1080/1343943X.2017.137157010.1080/1343943X.2017.1371570
Dlamini PJ Drought stress tolerance mechanisms and breeding effort in sugarcane: a review of progress and constraints in South Africa Plant Stress 2021 2 100027 10.1016/j.stress.2021.100027
Dlamini PJ (2021) Drought stress tolerance mechanisms and breeding effort in sugarcane: a review of progress and constraints in South Africa. Plant Stress 2:100027. 10.1016/j.stress.2021.10002710.1016/j.stress.2021.100027
Du YC Kawamitsu Y Nose A Hiyane S Murayama S Wasano K Uchida Y Effects of water stress on carbon exchange rate and activities of photosynthetic enzymes in leaves of sugarcane (Saccharum sp.) Func Plant Biol 1996 23 6 719 726 10.1071/PP9960719
Du YC, Kawamitsu Y, Nose A, Hiyane S, Murayama S, Wasano K, Uchida Y (1996) Effects of water stress on carbon exchange rate and activities of photosynthetic enzymes in leaves of sugarcane (Saccharum sp.). Func Plant Biol 23(6):719–726. 10.1071/PP996071910.1071/PP9960719
FAOSTAT (2022) Sugarcane area harvested. FAO. Retrieved May 12, 2022, from https://www.fao.org/faostat/en/#data/QCL
Ferreira TH Tsunada MS Bassi D Araújo P Mattiello L Guidelli GV Righetto GL Gonçalves VR Lakshmanan P Menossi M Sugarcane water stress tolerance mechanisms and its implications on developing biotechnology solutions Front Plant Sci 2017 8 1077 10.3389/fpls.2017.01077 28690620
Ferreira TH, Tsunada MS, Bassi D, Araújo P, Mattiello L, Guidelli GV, Righetto GL, Gonçalves VR, Lakshmanan P, Menossi M (2017) Sugarcane water stress tolerance mechanisms and its implications on developing biotechnology solutions. Front Plant Sci 8:1077. 10.3389/fpls.2017.0107728690620 10.3389/fpls.2017.01077
Franks PJ Doheny-Adams T Britton-Harper ZJ Gray JE Increasing water-use efficiency directly through genetic manipulation of stomatal density New Phytol 2015 207 1 188 195 10.1111/nph.13347 25754246
Franks PJ, Doheny-Adams T, Britton-Harper ZJ, Gray JE (2015) Increasing water-use efficiency directly through genetic manipulation of stomatal density. New Phytol 207(1):188–195. 10.1111/nph.1334725754246 10.1111/nph.13347
Glassop D Roessner U Bacic A Bonnett GD Changes in the sugarcane metabolome with stem development. Are they related to sucrose accumulation? Plant Cell Physiol 2007 48 4 573 584 10.1093/pcp/pcm027 17327259
Glassop D, Roessner U, Bacic A, Bonnett GD (2007) Changes in the sugarcane metabolome with stem development. Are they related to sucrose accumulation? Plant Cell Physiol 48(4):573–584. 10.1093/pcp/pcm02717327259 10.1093/pcp/pcm027
Hamid SS Wakayama M Soga T Tomita M Drying and extraction effects on three edible brown seaweeds for metabolomics J Appl Phycol 2018 30 6 3335 3350 10.1007/s10811-018-1614-z
Hamid SS, Wakayama M, Soga T, Tomita M (2018) Drying and extraction effects on three edible brown seaweeds for metabolomics. J Appl Phycol 30(6):3335–3350. 10.1007/s10811-018-1614-z10.1007/s10811-018-1614-z
Hamid SS Wakayama M Ichihara K Sakurai K Ashino Y Kadowaki R Soga T Tomita M Metabolome profiling of various seaweed species discriminates between brown, red, and green algae Planta 2019 249 1921 1947 10.1007/s00425-019-03134-1 30891648
Hamid SS, Wakayama M, Ichihara K, Sakurai K, Ashino Y, Kadowaki R, Soga T, Tomita M (2019) Metabolome profiling of various seaweed species discriminates between brown, red, and green algae. Planta 249:1921–1947. 10.1007/s00425-019-03134-130891648 10.1007/s00425-019-03134-1
Hamid SS Wakayama M Ashino Y Kadowaki R Soga T Tomita M Effect of blanching on the concentration of metabolites in two parts of Undaria pinnatifida, Wakame (leaf) and Mekabu (sporophyll) Algal Res 2020 47 101829 10.1016/j.algal.2020.101829
Hamid SS, Wakayama M, Ashino Y, Kadowaki R, Soga T, Tomita M (2020) Effect of blanching on the concentration of metabolites in two parts of Undaria pinnatifida, Wakame (leaf) and Mekabu (sporophyll). Algal Res 47:101829. 10.1016/j.algal.2020.10182910.1016/j.algal.2020.101829
Hare PD Cress WA Van Staden J Dissecting the roles of osmolyte accumulation during stress Plant Cell Environ 1998 21 6 535 553 10.1046/j.1365-3040.1998.00309.x
Hare PD, Cress WA, Van Staden J (1998) Dissecting the roles of osmolyte accumulation during stress. Plant Cell Environ 21(6):535–553. 10.1046/j.1365-3040.1998.00309.x10.1046/j.1365-3040.1998.00309.x
Hasan MM Alabdallah NM Alharbi BM Waseem M Yao G Liu XD Abd El-Gawad HG El-Yazied AA Ibrahim MFM Jahan MS Fang XW GABA: a key player in drought stress resistance in plants Int J Mol Sci 2021 22 18 10136 10.3390/ijms221810136 34576299
Hasan MM, Alabdallah NM, Alharbi BM, Waseem M, Yao G, Liu XD, Abd El-Gawad HG, El-Yazied AA, Ibrahim MFM, Jahan MS, Fang XW (2021) GABA: a key player in drought stress resistance in plants. Int J Mol Sci 22(18):10136. 10.3390/ijms22181013634576299 10.3390/ijms221810136
Hattori T Mitsuya S Fujiwara T Jagendorf AT Takabe T Tissue specificity of glycinebetaine synthesis in barley Plant Sci 2009 176 1 112 118 10.1016/j.plantsci.2008.10.003
Hattori T, Mitsuya S, Fujiwara T, Jagendorf AT, Takabe T (2009) Tissue specificity of glycinebetaine synthesis in barley. Plant Sci 176(1):112–118. 10.1016/j.plantsci.2008.10.00310.1016/j.plantsci.2008.10.003
Hong J Yang L Zhang D Shi J Plant metabolomics: an indispensable system biology tool for plant science Int J Mol Sci 2016 17 6 767 10.3390/ijms17060767 27258266
Hong J, Yang L, Zhang D, Shi J (2016) Plant metabolomics: an indispensable system biology tool for plant science. Int J Mol Sci 17(6):767. 10.3390/ijms1706076727258266 10.3390/ijms17060767
Horgan RP Kenny LC ‘Omic’technologies: genomics, transcriptomics, proteomics and metabolomics Obstet Gynaecol 2011 13 3 189 195 10.1576/toag.13.3.189.27672
Horgan RP, Kenny LC (2011) ‘Omic’technologies: genomics, transcriptomics, proteomics and metabolomics. Obstet Gynaecol 13(3):189–195. 10.1576/toag.13.3.189.2767210.1576/toag.13.3.189.27672
Jackson P Why are yields of sugarcane not increasing as much as sugar beet (or other crops)? Proc Int Soc Sug Cane Technol 2019 30 128 137
Jackson P (2019) Why are yields of sugarcane not increasing as much as sugar beet (or other crops)? Proc Int Soc Sug Cane Technol 30:128–137
Jackson P Henry RJ Kole C Erianthus Wild crop relatives. Genomic and breeding resources 2011 Berlin, Heidelberg Springer 97 107
Jackson P, Henry RJ (2011) Erianthus. In: Kole C (ed) Wild crop relatives. Genomic and breeding resources. Springer, Berlin, Heidelberg, pp 97–107. 10.1007/978-3-642-21102-7_5
Jackson P Robertson M Cooper M Hammer G The role of physiological understanding in plant breeding; from a breeding perspective Field Crops Res 1996 49 1 11 37 10.1016/S0378-4290(96)01012-X
Jackson P, Robertson M, Cooper M, Hammer G (1996) The role of physiological understanding in plant breeding; from a breeding perspective. Field Crops Res 49(1):11–37. 10.1016/S0378-4290(96)01012-X10.1016/S0378-4290(96)01012-X
Jackson P Basnayake J Inman-Bamber G Lakshmanan P Natarajan S Stokes C Genetic variation in transpiration efficiency and relationships between whole plant and leaf gas exchange measurements in Saccharum spp. and related germplasm J Exp Bot 2016 67 3 861 871 10.1093/jxb/erv505 26628517
Jackson P, Basnayake J, Inman-Bamber G, Lakshmanan P, Natarajan S, Stokes C (2016) Genetic variation in transpiration efficiency and relationships between whole plant and leaf gas exchange measurements in Saccharum spp. and related germplasm. J Exp Bot 67(3):861–871. 10.1093/jxb/erv50526628517 10.1093/jxb/erv505
Kim HK Verpoorte R Sample preparation for plant metabolomics Phytochem Anal 2010 21 1 4 13 10.1002/pca.1188 19904733
Kim HK, Verpoorte R (2010) Sample preparation for plant metabolomics. Phytochem Anal 21(1):4–13. 10.1002/pca.118819904733 10.1002/pca.1188
Kinnersley AM Turano FJ Gamma aminobutyric acid (GABA) and plant responses to stress Crit Rev Plant Sci 2000 19 6 479 509 10.1080/07352680091139277
Kinnersley AM, Turano FJ (2000) Gamma aminobutyric acid (GABA) and plant responses to stress. Crit Rev Plant Sci 19(6):479–509. 10.1080/0735268009113927710.1080/07352680091139277
Kumar R Bohra A Pandey AK Pandey MK Kumar A Metabolomics for plant improvement: status and prospects Front Plant Sci 2017 8 1302 10.3389/fpls.2017.01302 28824660
Kumar R, Bohra A, Pandey AK, Pandey MK, Kumar A (2017) Metabolomics for plant improvement: status and prospects. Front Plant Sci 8:1302. 10.3389/fpls.2017.0130228824660 10.3389/fpls.2017.01302
Langridge P Fleury D Making the most of ‘omics’ for crop breeding Trends Biotechnol 2011 29 1 33 40 10.1016/j.tibtech.2010.09.006 21030098
Langridge P, Fleury D (2011) Making the most of ‘omics’ for crop breeding. Trends Biotechnol 29(1):33–40. 10.1016/j.tibtech.2010.09.00621030098 10.1016/j.tibtech.2010.09.006
Li C Jackson P Lu X Xu C Cai Q Basnayake J Lakshmanan P Ghannoum O Fan Y Genotypic variation in transpiration efficiency due to differences in photosynthetic capacity among sugarcane-related clones J Exp Bot 2017 68 9 2377 2385 10.1093/jxb/erx107 28444313
Li C, Jackson P, Lu X, Xu C, Cai Q, Basnayake J, Lakshmanan P, Ghannoum O, Fan Y (2017) Genotypic variation in transpiration efficiency due to differences in photosynthetic capacity among sugarcane-related clones. J Exp Bot 68(9):2377–2385. 10.1093/jxb/erx10728444313 10.1093/jxb/erx107
Liu J Basnayake J Jackson PA Chen X Zhao J Zhao P Yang L Bai Y Xia H Zan F Qin W Yang K Yao L Zhao L Zhu J Lakshmanan P Zhao X Fan Y Growth and yield of sugarcane genotypes are strongly correlated across irrigated and rainfed environments Field Crops Res 2016 196 418 425 10.1016/j.fcr.2016.07.022
Liu J, Basnayake J, Jackson PA, Chen X, Zhao J, Zhao P, Yang L, Bai Y, Xia H, Zan F, Qin W, Yang K, Yao L, Zhao L, Zhu J, Lakshmanan P, Zhao X, Fan Y (2016) Growth and yield of sugarcane genotypes are strongly correlated across irrigated and rainfed environments. Field Crops Res 196:418–425. 10.1016/j.fcr.2016.07.02210.1016/j.fcr.2016.07.022
Marchiori PE Machado EC Ribeiro RV Photosynthetic limitations imposed by self-shading in field-grown sugarcane varieties Field Crops Res 2014 155 30 37 10.1016/j.fcr.2013.09.025
Marchiori PE, Machado EC, Ribeiro RV (2014) Photosynthetic limitations imposed by self-shading in field-grown sugarcane varieties. Field Crops Res 155:30–37. 10.1016/j.fcr.2013.09.02510.1016/j.fcr.2013.09.025
Marchiori PE Machado EC Sales CR Espinoza-Núñez E Magalhães Filho JR Souza GM Pires RGM Ribeiro RV Physiological plasticity is important for maintaining sugarcane growth under water deficit Front Plant Sci 2017 8 2148 10.3389/fpls.2017.02148 29326744
Marchiori PE, Machado EC, Sales CR, Espinoza-Núñez E, Magalhães Filho JR, Souza GM, Pires RGM, Ribeiro RV (2017) Physiological plasticity is important for maintaining sugarcane growth under water deficit. Front Plant Sci 8:2148. 10.3389/fpls.2017.0214829326744 10.3389/fpls.2017.02148
Meinzer FC Grantz DA Stomatal control of transpiration from a developing sugarcane canopy Plant Cell Environ 1989 12 6 635 642 10.1111/j.1365-3040.1989.tb01232.x
Meinzer FC, Grantz DA (1989) Stomatal control of transpiration from a developing sugarcane canopy. Plant Cell Environ 12(6):635–642. 10.1111/j.1365-3040.1989.tb01232.x10.1111/j.1365-3040.1989.tb01232.x
Miyashita Y Good AG Contribution of the GABA shunt to hypoxia-induced alanine accumulation in roots of Arabidopsis thaliana Plant Cell Physiol 2008 49 1 92 102 10.1093/pcp/pcm171 18077464
Miyashita Y, Good AG (2008) Contribution of the GABA shunt to hypoxia-induced alanine accumulation in roots of Arabidopsis thaliana. Plant Cell Physiol 49(1):92–102. 10.1093/pcp/pcm17118077464 10.1093/pcp/pcm171
Natarajan S Basnayake J Lakshmanan P Fukai S Limited contribution of water availability in genotype-by-environment interaction in sugarcane yield and yield components J Agron Crop Sci 2020 206 6 665 678 10.1111/jac.12407
Natarajan S, Basnayake J, Lakshmanan P, Fukai S (2020) Limited contribution of water availability in genotype-by-environment interaction in sugarcane yield and yield components. J Agron Crop Sci 206(6):665–678. 10.1111/jac.1240710.1111/jac.12407
Natarajan S Basnayake J Lakshmanan P Fukai S Genotypic variation in intrinsic transpiration efficiency correlates with sugarcane yield under rainfed and irrigated field conditions Physiol Plant 2021 172 2 976 989 10.1111/ppl.13221 32997338
Natarajan S, Basnayake J, Lakshmanan P, Fukai S (2021) Genotypic variation in intrinsic transpiration efficiency correlates with sugarcane yield under rainfed and irrigated field conditions. Physiol Plant 172(2):976–989. 10.1111/ppl.1322132997338 10.1111/ppl.13221
Ogura T Wakayama M Ashino Y Kadowaki R Sato M Soga T Tomita M Effects of feed crops and boiling on chicken egg yolk and white determined by a metabolome analysis Food Chem 2020 327 127077 10.1016/j.foodchem.2020.127077 32485660
Ogura T, Wakayama M, Ashino Y, Kadowaki R, Sato M, Soga T, Tomita M (2020) Effects of feed crops and boiling on chicken egg yolk and white determined by a metabolome analysis. Food Chem 327:127077. 10.1016/j.foodchem.2020.12707732485660 10.1016/j.foodchem.2020.127077
Ozeki K Miyazawa Y Sugiura D Rapid stomatal closure contributes to higher water use efficiency in major C4 compared to C3 Poaceae crops Plant Physiol 2022 189 1 188 203 10.1093/plphys/kiac040 35134220
Ozeki K, Miyazawa Y, Sugiura D (2022) Rapid stomatal closure contributes to higher water use efficiency in major C4 compared to C3 Poaceae crops. Plant Physiol 189(1):188–203. 10.1093/plphys/kiac04035134220 10.1093/plphys/kiac040
Ozturk M Turkyilmaz-Unal B García-Caparrós P Khursheed A Gul A Hasanuzzaman M Osmoregulation and its actions during the drought stress in plants Physiol Plant 2021 172 2 1321 1335 10.1111/ppl.13297 33280137
Ozturk M, Turkyilmaz-Unal B, García-Caparrós P, Khursheed A, Gul A, Hasanuzzaman M (2021) Osmoregulation and its actions during the drought stress in plants. Physiol Plant 172(2):1321–1335. 10.1111/ppl.1329733280137 10.1111/ppl.13297
Perlo V Furtado A Botha FC Margarido GR Hodgson-Kratky K Choudhary H Gladden J Simmons B Henry RJ Transcriptome and metabolome integration in sugarcane through culm development Food Energy Secur 2022 11 4 e421 10.1002/fes3.421
Perlo V, Furtado A, Botha FC, Margarido GR, Hodgson-Kratky K, Choudhary H, Gladden J, Simmons B, Henry RJ (2022) Transcriptome and metabolome integration in sugarcane through culm development. Food Energy Secur 11(4):e421. 10.1002/fes3.42110.1002/fes3.421
Pitaloka MK Caine RS Hepworth C Harrison EL Sloan J Chutteang C Induced genetic variations in stomatal density and size of rice strongly affects water use efficiency and responses to drought stresses Front Plant Sci 2022 13 801706 10.3389/fpls.2022.801706 35693177
Pitaloka MK, Caine RS, Hepworth C, Harrison EL, Sloan J, Chutteang C et al (2022) Induced genetic variations in stomatal density and size of rice strongly affects water use efficiency and responses to drought stresses. Front Plant Sci 13:801706. 10.3389/fpls.2022.80170635693177 10.3389/fpls.2022.801706
Popova TN de Carvalho MÂAP Citrate and isocitrate in plant metabolism Biochim Biophys Acta (BBA)- Bioenergetics 1998 1364 3 307 325 10.1016/S0005-2728(98)00008-5 9630693
Popova TN, de Carvalho MÂAP (1998) Citrate and isocitrate in plant metabolism. Biochim Biophys Acta (BBA)- Bioenergetics 1364(3):307–325. 10.1016/S0005-2728(98)00008-59630693 10.1016/S0005-2728(98)00008-5
Prabu G Kawar PG Pagariya MC Prasad DT Identification of water deficit stress upregulated genes in sugarcane Plant Mol Biol Rep 2011 29 291 304 10.1007/s11105-010-0230-0
Prabu G, Kawar PG, Pagariya MC, Prasad DT (2011) Identification of water deficit stress upregulated genes in sugarcane. Plant Mol Biol Rep 29:291–304. 10.1007/s11105-010-0230-010.1007/s11105-010-0230-0
Raggi V Changes in free amino acids and osmotic adjustment in leaves of water-stressed bean Physiol Plant 1994 91 3 427 434 10.1111/j.1399-3054.1994.tb02970.x
Raggi V (1994) Changes in free amino acids and osmotic adjustment in leaves of water-stressed bean. Physiol Plant 91(3):427–434. 10.1111/j.1399-3054.1994.tb02970.x10.1111/j.1399-3054.1994.tb02970.x
Ravanel S Gakière B Job D Douce R The specific features of methionine biosynthesis and metabolism in plants Proc Natl Acad Sci USA 1998 95 13 7805 7812 10.1073/pnas.95.13.7805 9636232
Ravanel S, Gakière B, Job D, Douce R (1998) The specific features of methionine biosynthesis and metabolism in plants. Proc Natl Acad Sci USA 95(13):7805–7812. 10.1073/pnas.95.13.78059636232 10.1073/pnas.95.13.7805
Rhodes D Handa S Bressan RA Metabolic changes associated with adaptation of plant cells to water stress Plant Physiol 1986 82 4 890 903 10.1104/pp.82.4.890 16665163
Rhodes D, Handa S, Bressan RA (1986) Metabolic changes associated with adaptation of plant cells to water stress. Plant Physiol 82(4):890–903. 10.1104/pp.82.4.89016665163 10.1104/pp.82.4.890
Robertson MJ Inman-Bamber NG Muchow RC Wood AW Physiology and productivity of sugarcane with early and mid-season water deficit Field Crops Res 1999 64 3 211 227 10.1016/S0378-4290(99)00042-8
Robertson MJ, Inman-Bamber NG, Muchow RC, Wood AW (1999) Physiology and productivity of sugarcane with early and mid-season water deficit. Field Crops Res 64(3):211–227. 10.1016/S0378-4290(99)00042-810.1016/S0378-4290(99)00042-8
Sage RF, Peixoto MM, Sage TL (2013) Photosynthesis in sugarcane. In: Moore PH, Botha FC (eds) Sugarcane: Physiology, biochemistry, and functional biology.Wiley, Iowa, pp121–154. 10.1002/9781118771280.ch6
Sakamoto A Murata N The role of glycine betaine in the protection of plants from stress: clues from transgenic plants Plant Cell Environ 2002 25 2 163 171 10.1046/j.0016-8025.2001.00790.x 11841661
Sakamoto A, Murata N (2002) The role of glycine betaine in the protection of plants from stress: clues from transgenic plants. Plant Cell Environ 25(2):163–171. 10.1046/j.0016-8025.2001.00790.x11841661 10.1046/j.0016-8025.2001.00790.x
Sapes G Sala A Relative water content consistently predicts drought mortality risk in seedling populations with different morphology, physiology and times to death Plant Cell Environ 2021 44 10 3322 3335 10.1111/pce.14149 34251033
Sapes G, Sala A (2021) Relative water content consistently predicts drought mortality risk in seedling populations with different morphology, physiology and times to death. Plant Cell Environ 44(10):3322–3335. 10.1111/pce.1414934251033 10.1111/pce.14149
Silvente S Sobolev AP Lara M Metabolite adjustments in drought tolerant and sensitive soybean genotypes in response to water stress PLoS One 2012 7 6 e38554 10.1371/journal.pone.0038554 22685583
Silvente S, Sobolev AP, Lara M (2012) Metabolite adjustments in drought tolerant and sensitive soybean genotypes in response to water stress. PLoS One 7(6):e38554. 10.1371/journal.pone.003855422685583 10.1371/journal.pone.0038554
Singels A Paraskevopoulos AL Mashabela ML Farm level decision support for sugarcane irrigation management during drought Agric Water Manag 2019 222 274 285 10.1016/j.agwat.2019.05.048
Singels A, Paraskevopoulos AL, Mashabela ML (2019) Farm level decision support for sugarcane irrigation management during drought. Agric Water Manag 222:274–285. 10.1016/j.agwat.2019.05.04810.1016/j.agwat.2019.05.048
Singh RK Sood P Prasad A Prasad M Advances in omics technology for improving crop yield and stress resilience Plant Breed 2021 140 5 719 731 10.1111/pbr.12963
Singh RK, Sood P, Prasad A, Prasad M (2021) Advances in omics technology for improving crop yield and stress resilience. Plant Breed 140(5):719–731. 10.1111/pbr.1296310.1111/pbr.12963
Strock CF Schneider HM Lynch JP Anatomics: high-throughput phenotyping of plant anatomy Trends Plant Sci 2022 27 6 520 523 10.1016/j.tplants.2022.02.009 35307268
Strock CF, Schneider HM, Lynch JP (2022) Anatomics: high-throughput phenotyping of plant anatomy. Trends Plant Sci 27(6):520–523. 10.1016/j.tplants.2022.02.00935307268 10.1016/j.tplants.2022.02.009
Sugimoto M Kawakami M Robert M Soga T Tomita M Bioinformatics tools for mass spectroscopy-based metabolomic data processing and analysis Curr Bioinform 2012 7 1 96 108 10.2174/157489312799304431 22438836
Sugimoto M, Kawakami M, Robert M, Soga T, Tomita M (2012) Bioinformatics tools for mass spectroscopy-based metabolomic data processing and analysis. Curr Bioinform 7(1):96–108. 10.2174/15748931279930443122438836 10.2174/157489312799304431
Villate A San Nicolas M Gallastegi M Aulas PA Olivares M Usobiaga A Etxebarria N Aizpurua-Olaizola O Metabolomics as a prediction tool for plants performance under environmental stress Plant Sci 2021 303 110789 10.1016/j.plantsci.2020.110789 33487364
Villate A, San Nicolas M, Gallastegi M, Aulas PA, Olivares M, Usobiaga A, Etxebarria N, Aizpurua-Olaizola O (2021) Metabolomics as a prediction tool for plants performance under environmental stress. Plant Sci 303:110789. 10.1016/j.plantsci.2020.11078933487364 10.1016/j.plantsci.2020.110789
Vital CE Giordano A de Almeida SE Rhys Williams TC Mesquita RO Vidigal PMP de Santana LA Pacheco TG Rogalski M de Oliveira Ramos HJ Loureiro ME An integrative overview of the molecular and physiological responses of sugarcane under drought conditions Plant Mol Biol 2017 94 577 594 10.1007/s11103-017-0611-y 28409321
Vital CE, Giordano A, de Almeida SE, Rhys Williams TC, Mesquita RO, Vidigal PMP, de Santana LA, Pacheco TG, Rogalski M, de Oliveira Ramos HJ, Loureiro ME (2017) An integrative overview of the molecular and physiological responses of sugarcane under drought conditions. Plant Mol Biol 94:577–594. 10.1007/s11103-017-0611-y28409321 10.1007/s11103-017-0611-y
von Caemmerer S Furbank RT The C4 pathway: an efficient CO2 pump Photosyn Res 2003 77 191 207 10.1023/A:1025830019591
von Caemmerer S, Furbank RT (2003) The C4 pathway: an efficient CO2 pump. Photosyn Res 77:191–207. 10.1023/A:102583001959110.1023/A:1025830019591
Wakayama M Hirayama A Soga T Capillary electrophoresis-mass spectrometry Metabonom Methods Protoc 2015 10.1007/978-1-4939-2377-9_9
Wakayama M, Hirayama A, Soga T (2015) Capillary electrophoresis-mass spectrometry. Metabonom Methods Protoc. 10.1007/978-1-4939-2377-9_910.1007/978-1-4939-2377-9_9
Wang C Fan L Gao H Wu X Li J Lv G Gong B Polyamine biosynthesis and degradation are modulated by exogenous gamma-aminobutyric acid in root-zone hypoxia-stressed melon roots Plant Physiol Biochem 2014 82 17 26 10.1016/j.plaphy.2014.04.018 24869798
Wang C, Fan L, Gao H, Wu X, Li J, Lv G, Gong B (2014) Polyamine biosynthesis and degradation are modulated by exogenous gamma-aminobutyric acid in root-zone hypoxia-stressed melon roots. Plant Physiol Biochem 82:17–26. 10.1016/j.plaphy.2014.04.01824869798 10.1016/j.plaphy.2014.04.018
Watanabe K Nakabaru M Taira E Ueno M Kawamitsu Y Relationships between nutrients and sucrose concentrations in sugarcane juice and use of juice analysis for nutrient diagnosis in Japan Plant Prod Sci 2016 19 2 215 222 10.1080/1343943X.2015.1128106
Watanabe K, Nakabaru M, Taira E, Ueno M, Kawamitsu Y (2016) Relationships between nutrients and sucrose concentrations in sugarcane juice and use of juice analysis for nutrient diagnosis in Japan. Plant Prod Sci 19(2):215–222. 10.1080/1343943X.2015.112810610.1080/1343943X.2015.1128106
Watt D Butterfield M Huckett B Henry RJ Kole C Proteomics and metabolomics Genetics, genomics and breeding of sugarcane 2010 Enfield Science Publication 193 228
Watt D, Butterfield M, Huckett B (2010) Proteomics and metabolomics. In: Henry RJ, Kole C (eds) Genetics, genomics and breeding of sugarcane. Science Publication, Enfield, pp 193–228
Weaver LM Herrmann KM Dynamics of the shikimate pathway in plants Trends Plant Sci 1997 2 9 346 351 10.1016/S1360-1385(97)84622-5
Weaver LM, Herrmann KM (1997) Dynamics of the shikimate pathway in plants. Trends Plant Sci 2(9):346–351. 10.1016/S1360-1385(97)84622-510.1016/S1360-1385(97)84622-5
Wei X Jackson P Addressing slow rates of long-term genetic gain in sugarcane Proc Int Soc Sugar Cane Technol 2016 29 1923 1930
Wei X, Jackson P (2016) Addressing slow rates of long-term genetic gain in sugarcane. Proc Int Soc Sugar Cane Technol 29:1923–1930
Westgate ME Boyer JS Osmotic adjustment and the inhibition of leaf, root, stem and silk growth at low water potentials in maize Planta 1985 164 540 549 10.1007/BF00395973 24248230
Westgate ME, Boyer JS (1985) Osmotic adjustment and the inhibition of leaf, root, stem and silk growth at low water potentials in maize. Planta 164:540–549. 10.1007/BF0039597324248230 10.1007/BF00395973
Wu S, Zhao B (2017) Using clear nail polish to make Arabidopsis epidermal impressions for measuring the change of stomatal aperture size in immune response. In: Shan L, He P (eds) Plant pattern recognition receptors. Methods and protocols. Methods Mol Biol 1578: 243–248. 10.1007/978-1-4939-6859-6_20
Xu B Long Y Feng X Zhu X Sai N Chirkova L Betts A Herrmann J Edwards EJ Okamoto M Hedrich R Gilliham M GABA signalling modulates stomatal opening to enhance plant water use efficiency and drought resilience Nat Commun 2021 12 1 1952 10.1038/s41467-021-21694-3 33782393
Xu B, Long Y, Feng X, Zhu X, Sai N, Chirkova L, Betts A, Herrmann J, Edwards EJ, Okamoto M, Hedrich R, Gilliham M (2021) GABA signalling modulates stomatal opening to enhance plant water use efficiency and drought resilience. Nat Commun 12(1):1952. 10.1038/s41467-021-21694-333782393 10.1038/s41467-021-21694-3
Ye ZP Ling Y Yu Q Duan HL Kang HJ Huang GM Duan SH Chen XM Liu YG Zhou SX Quantifying light response of leaf-scale water-use efficiency and its interrelationships with photosynthesis and stomatal conductance in C3 and C4 species Front Plant Sci 2020 11 374 10.3389/fpls.2020.00374 32411151
Ye ZP, Ling Y, Yu Q, Duan HL, Kang HJ, Huang GM, Duan SH, Chen XM, Liu YG, Zhou SX (2020) Quantifying light response of leaf-scale water-use efficiency and its interrelationships with photosynthesis and stomatal conductance in C3 and C4 species. Front Plant Sci 11:374. 10.3389/fpls.2020.0037432411151 10.3389/fpls.2020.00374
Zhao D Glaz B Comstock JC Sugarcane leaf photosynthesis and growth characters during development of water-deficit stress Crop Sci 2013 53 3 1066 1075 10.2135/cropsci2012.09.0554
Zhao D, Glaz B, Comstock JC (2013) Sugarcane leaf photosynthesis and growth characters during development of water-deficit stress. Crop Sci 53(3):1066–1075. 10.2135/cropsci2012.09.055410.2135/cropsci2012.09.0554
Zhao P Jackson PA Basnayake J Liu J Chen X Zhao J Zhao X Bai Y Yang L Zan F Yang K Xia H Qin W Zhao L Yao L Lakshmanan P Fan Y Genetic variation in sugarcane for leaf functional traits and relationships with cane yield, in environments with varying water stress Field Crops Res 2017 213 143 153 10.1016/j.fcr.2017.08.004
Zhao P, Jackson PA, Basnayake J, Liu J, Chen X, Zhao J, Zhao X, Bai Y, Yang L, Zan F, Yang K, Xia H, Qin W, Zhao L, Yao L, Lakshmanan P, Fan Y (2017) Genetic variation in sugarcane for leaf functional traits and relationships with cane yield, in environments with varying water stress. Field Crops Res 213:143–153. 10.1016/j.fcr.2017.08.00410.1016/j.fcr.2017.08.004
