The Effect of Water Stress on Remobilization of Pre-anthesis Stored Assimilates to Grains in Wheat

Abstract
Five bread wheat (Triticum aestivum L.) cultivars including Kavir, Pishtaz, Niknejad, Omid and Roshan were evaluated in a split plot experiment based on randomized complete block design with three replications. Water stress and well-watered conditions were assigned to the main plots and varieties to the subplots. Water stress was imposed by withholding irrigation at the booting stage. During a period of 45 days, which spanned before and after anthesis, plants were sampled and changes in dry matter of peduncle and penultimate internodes were assessed. An increase in grain weight was accompanied with a decrease in peduncle and penultimate internodes dry matter, which could be attributed to the remobilization of stored assimilates to grains. Remobilization of stored assimilates was relatively higher under water-stress condition as compared with the well-watered environment. Under water stress condition, tall cultivars remobilized more assimilates than the dwarf genotypes. In the well-watered plots, remobilization percentage from peduncle was more than penultimate internodes in tall varieties as compared with the dwarf varieties. On the other hand, under water stress condition, more assimilates were remobilized from penultimate than the peduncle in dwarf varieties as compared to the tall genotypes. In the dwarf genotypes assimilates remobilization was reduced under water stress conditions while it was increased in the tall cultivars.