Contribution of Spike and Leaves Photosynthesis and Soluble Stem Carbohydrates Remobilization in Grain Yield Formation in Two Bread Wheat Cultivars under Post- Anthesis Stress conditions

In most researches that carried out to evaluate the contribution of current photosynthesis in grain yield formation, the role of spike is less considered. Therefore, this study was carried out to compare the role of spike and leaves photosynthesis and soluble stem carbohydrates remobilization under different water stress treatments at cell division and grain filling stages, on grain yield formation and some related traits in two bread wheat cultivars (Marvdasht and Zagros). Factorial arrangements in randomized complete block design with three replications was used. Inhibiting of spike and leaves photosynthesis treatments at the beginning of grain filling (14 days after anthesis) and water stress treatments at the beginning of grain filling (14 days after anthesis) and grain filling stages were applied. Water stress significantly decreased grain yield in two bread wheat cultivars. Grain yield reduction under water stress in cv. Marvdasht cultivar was greater. Inhibition of whole plant and spike photosynthesis with chemical desiccant (KI) did not simulate drought stress, however, the effect of water stress was intensified by inhibiting current photosynthesis and caused more reduction of grain yield in cv. Zagros. These results showed that under water stress treatments, higher yield stability of cv. Zagros could be related to greater resistance of its photosynthetic system. Inhibition of whole plant and spike photosynthesis at the beginning of grain filling showed that contributions of spike and leaves photosynthesis and soluble stem carbohydrates remobilization in grain yield formation of two bread wheat cultivars were 63%, 43% and 25%, respectively.