Abstract
The aim of this study is to study the effects of water deficit on physiologic parameters related to yield in two wheat cultivars (Triticum aestivum L.), Marvdasht and Zagros (sensitive and tolerant to terminal season drought, respectively) grown in pots under well watered and water-stressed starting from anthesis to maturity. Water stress resulted in a marked increase in leaf proline content of the drought-tolerant that led to alleviate the deleterious effect of water stress whereas, a slightly increment at the end of grain development observed in drought sensitive cv. The effect of drought on grain yield was primarily due to the significant reduction in grain weight, particularly in drought-sensitive. The results indicate that grain filling processes under water restriction are limited by low substrate availability and reduced synthesis capacity of the sink. Hence, the main physiological factor associated with yield stability of Zagros under drought stress may be attributed to the capacity for chloroplast activity in the flag leaf. The higher assimilate in Zagros grains under drought could also be related to drought resistance. These results raise the possibility that water stress-induced elevated levels of proline in Zagros contribute to reduced harmful stress during grain filling. Key words: Assimilate, flag leaves, grain yield, proline, soluble proteins, wheat (Triticum aestivum L.).
Highlights
Research on biochemical changes that occur during leaf senescence has focused on loss of photosynthetic pigments, degradation of protein, and reabsorption of mineral nutrients
Water stress resulted in a marked increase in leaf proline content of the droughttolerant that led to alleviate the deleterious effect of water stress whereas, a slightly increment at the end of grain development observed in drought sensitive cv
The amounts of soluble proteins reduced with time in both treatments (Figure 1C, D), considerable differences were detected between treatments, as substantial reduction occurred in both cultivars under water stress compared with the control treatment
Summary
Research on biochemical changes that occur during leaf senescence has focused on loss of photosynthetic pigments, degradation of protein, and reabsorption of mineral nutrients. To cope with drought stress, plants respond with physiological and biochemical changes. These changes aim at the retention of water in spite of the high external osmoticum and the maintenance of photosynthetic activity, while stomatal opening is reduced to counter water loss. Accumulation of low molecular compounds, according to the metabolic responses has drawn much attention. Adaptation to all these stresses is associated with metabolic adjustments that lead to the accumulation of several organic solutes like sugars, polyols, betaines and proline (Ashraf, 2004; Irigoyen et al, 1992; Kohl et al, 1991). Such study will provide valuable information that can be used for genetic basis of improvement of wheat to enhance yield and quality under stress conditions
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