Osmotic adjustment and solutes in leaves of wheat (Triticum aestivum L.) during water deficit

[Truncated abstract] Osmotic adjustment (OA) contributes to plant tolerance of water deficit (WD). This study evaluated OA in three wheat (Triticum aestivum L.) cultivars under WD, in controlled-environment, field, and laboratory studies, with the objective to identify the solutes involved with regard to differences in duration of WD, stage of plant development, and cultivars, and whether with development of WD the patterns of accumulation differ amongst solutes. Leaf OA and solutes in cultivars Hartog (high OA) and Sunco (low OA) were evaluated at the reproductive stage in a controlled environment (Chapter 3). OA in Hartog was 5-times greater than in Sunco. At 21 d, K+ accounted for 12% of OA in Hartog and 48% in Sunco. Glycinebetaine and proline also increased under WD, but these were not significant osmotica after 21 d of drying. Hartog accumulated dry matter faster than Sunco under WD, and this was consistent with greater water use in Hartog than in Sunco. To identify the development of solute concentrations, WD was imposed on Hartog at the reproductive stage in a controlled environment (Chapter 3). OA increased curvilinearly with time during 37 d of drying. K+ increased up to 16 d and then decreased towards 37 d. Glycinebetaine, proline, fructose, and glucose increased gradually during the drying cycle, but each had a different pattern of accumulation. K+ was the major contributor to OA (54%) up to 30 d, whereas glycinebetaine, proline and glucose (~20%) were major contributors later. Leaf OA and solutes in Hartog and Sunco subjected to WD were evaluated at the grain filling stage in a controlled environment (Chapter 4). Leaf OA was evident in Hartog (2.1 MPa) and Sunco (2.6 MPa). K+, Na+, and Cl-, contributed (up to 27%) of leaf OA. Data on organic solutes were unavailable. A field experiment with Hartog and Mulgara (high OA) and Sunco (low OA), showed leaf OA occurred in these cultivars at 14 and 28 d of WD imposed during the grain filling stage.