Investigation the drought stress effects at the end of season on yield and transfer amount of stem soluble carbohydrates and grain yield of two wheat cultivars

Remobilization and retransfer of the stored Carbon from vegetative tissues to the grain in monocarpic plants requires the initiation of whole plant senescence by an unknown mechanism. This study examined the relationship between the senescence induced by water stress and C remobilization during grain filling. Two wheat cultivars, Marvdasht and Zagros (sensitive and tolerant to terminal season drought, respectively) grown at a day:night temperature of 15:22°C from anthesis were compared as well watered treatments control (Field Capacity) and water deficit treatments 50% FC imposed either from anthesis to 14 days later (WS1) or from 14 days after anthesis to physiological maturity (WS2). The experiment was conducted into the plastic flowerpots in a greenhouse and a factorial RCBD with three replications. Results showed that water stress treatment, both at WS1 and WS2, facilitated the reduction in concentration of total soluble sugars in the internodes and promoted the remobilization of pre-stored C from two internodes to grains. WS2 treatment resulted in more deleterious effect on grain yield than WS1 treatment in both cultivars and led to a smaller kernels and lesser aerial biomass at maturity time. The results of this research showed that the senescence and the stored compounds remobilization promoted by moisture stress during grain filling are coupled processes in wheat, the amounts of soluble sugars in the stem is more important than sugar remobilization efficiency. Varietal differences in the extent of such studied traits existed and it would be advantageous to select genotypes with greater capacity to store and transfer under water deficit conditions.