Pattern of solutes accumulated during leaf osmotic adjustment as related to duration of water deficit for wheat at the reproductive stage

• Published in: Plant physiology and biochemistry 2011-10, Vol.49 (10), p.1126-1137
• Main Authors: Nio, S.A., Cawthray, G.R., Wade, L.J., Colmer, T.D.
• Format: Article
• Language: English
• Subjects: Betaine - metabolism; Biological and medical sciences; Chlorides - metabolism; Dehydration; Drought stress; Fructose - metabolism; Fundamental and applied biological sciences. Psychology; Glucose; Glucose - metabolism; Glycinebetaine; Osmosis; Plant Leaves - genetics; Plant Leaves - growth & development; Plant Leaves - metabolism; Plant Leaves - physiology; Plant physiology and development; Plant Transpiration; Potassium - metabolism; Proline; Proline - metabolism; Reproduction; Sodium - metabolism; Soil - chemistry; Soil water extraction; Sucrose - metabolism; Triticum - genetics; Triticum - growth & development; Triticum - metabolism; Triticum - physiology; Water - metabolism
• ISSN: 0981-9428; 1873-2690
• DOI: 10.1016/j.plaphy.2011.05.011

This study examined expression of osmotic adjustment (OA) and accumulation of solutes in wheat (Triticum aestivum L.) leaves in response to water deficit (WD) imposed at the reproductive stage. Two contrasting cultivars, Hartog and Sunco (putatively high and low in OA capacity, respectively), were grown in deep (viz. 80 cm) pots in a controlled environment. In a sandy substrate, leaf OA was 5-times greater in Hartog compared with Sunco. At 21 d of WD treatment, K+ only accounted for 12% of OA in Hartog and 48% in Sunco with less OA (i.e. tissue K+ led to different proportions owing to different magnitudes of OA). Glycinebetaine and proline also increased under WD, but these were not significant osmotica on a whole tissue basis. Hartog accumulated dry matter faster than Sunco under WD, and this was consistent with greater water extraction by Hartog than by Sunco. In a second experiment on Hartog, with loam added to the sand to increase water-holding capacity and thus enable a longer draw-down period, leaf OA increased to 0.37 MPa at 37 d of withholding water. K+ increased up to 16 d of drying and then decreased towards 37 d. Glycinebetaine, proline, glucose and fructose all increased during the draw-down period, although with different dynamics; e.g. glycinebetaine increased linearly whereas glucose showed an exponential increase. By contrast, sucrose declined. K+ was the major contributor to OA (viz. 54%) up to 30 d of drying, whereas glycinebetaine, proline and glucose were major contributors later (at d 37 these organic solutes each accounted for 19, 21 and 21% of OA). Thus, the various solutes that contributed to leaf OA in wheat cv. Hartog accumulated at different times as WD developed. ► Wheat genotypes differ in osmotic adjustment, soil water extraction, and growth during water deficit, even in a sandy soil. ► Leaf osmotic adjustment in wheat was better expressed with duration of water deficit and in a drying sandy-loam than in sand. ► Inorganic and organic solutes contributed, with different dynamics and levels, to leaf osmotic adjustment in wheat. ► Glycinebetaine contributed to leaf osmotic adjustment in wheat; adding to earlier emphasis on K+, proline and sugars.