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With increasingly erratic rainfall patterns particularly in drought-prone production systems, the capacity of plants to recover productively from drought spells becomes an important feature for yield stability in rainfed agriculture. Consequently, effects of water management at the stem elongation stage on partitioning and remobilization of dry matter, alteration in photosynthesis and water-use efficiency (WUE), and yield components of wheat plants were studied in a glasshouse pot experiment. The plants were subjected to three soil moisture regimes: well watered during all phenological stages (WW), drought affected during stem elongation and post-anthesis stages (DD) and drought affected during stem elongation and rewatered at post-anthesis stage (DW). Total dry weight substantially decreased by both drought treatments. However, DD plants allocated relatively higher assimilates to roots whereas DW plants remobilized them to the grains. Drought applications resulted in a decrease of grain yield and thousand grain weight while reduction was more pronounced in DD treatment. Relative contribution of post-anthesis photosynthesis to dry matter formation in grain was higher in WW treatment (72.6 %) than DD (68.5 %) and DW (68.2 %) treatments. Photosynthetic rate, gas exchange and transpiration decreased whereas leaf (photosynthetic) and plant level WUE increased with drought applications. However, all these parameters were rapidly and completely reversed by rewatering. Our findings showed that partitioning of dry weight to grain increases with rewatering of wheat plants subjected to drought during stem elongation phase, but the relative contributions of remobilization of stem reserves and postanthesis photosynthesis to grain did not change. Moreover, rewatering of plants at booting stage after a drought period lead to full recovery in photosynthesis and WUE, and a significant although partial recovery of yield components, such as grain yield, TGW and harvest index.

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Wheat (T. aestivum) has a crucial role for human diet especially in developing countries. Changes in precipitation intensity, amounts and patterns restrict wheat growth and productivity under rainfed conditions. Thus, assessment of drought effects during growth stages of wheat on grain yield and quality traits has substantial importance. Grain filling stage, coincides with early spring when the rainfall pattern highly variable, was considered in this study to evaluate effects of drought conditions on yield and quality of 16 wheat genotypes and determine superior varieties. Drought treatment inhibited plant height (5.5 %), 1000 grain weight (9.2 %) and grain yield (17.7 %) while harvest index increased (8.5 %). However, there was no significant effect of drought conditions on grains number spike -1 and spike numbers m -2 . Protein content increased (31.6 %) in all genotypes, while the Zeleny sedimentation significantly decreased (8.2 %) with drought treatments during both growing seasons. Cultivars Pandas and Meta had higher grain yield under drought stress in both years whereas Line-28 and Pandas had better quality properties.

Plant responses to soil drying and the metabolic basis of drought‐induced limitations in stomatal opening are still being discussed. In this study, we investigate the roles of root‐born chemical and hydraulic signals on stomatal regulation in wheat genotypes as affected by soil drought and vapour pressure deficit. Twelve consecutive pot experiments were carried out in a glasshouse. Two bread wheat cultivars (Gönen and Basribey) were subjected to drought under high and low vapour pressure deficit (VPD) in a growth chamber. Total dry matter, specific leaf area, xylem ABA content, xylem osmotic potential, xylem pH, root water potential (RWP), stomatal conductance, leaf ABA content and photosynthetic activity were determined daily during 6 days after the onset of treatments (DAT). In the first phase of drought stress, soil drying induced an increase in the xylem ABA with a peak 3 DAT while RWP drastically decreased during the same period. Then the osmotic potential of leaves decreased and leaf ABA content increased 4 DAT. A similar peak was observed for stomatal conductance during the early stress phase, and it became stable and significantly higher than in well‐watered conditions especially in high vapour deficit conditions (H‐VPD). Furthermore, xylem pH and xylem osmotic potential appeared to be mostly associated with atmospheric moisture content than soil water availability. The results are discussed regarding possible drought adaptation of wheat under different atmospheric humidity.

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