The effect of foliar application of Indole-3-Acetic Acid (IAA) and roles of ear photosynthesis on grain yield production of two wheat cultivars (Triticum aestivum L.) under post anthesis water deficit

Plant growth regulators are the main factors in formation of grain yield. But their physiological roles are not well known. In example, about the roles of IAA in grains growth regulations are not similar viewpoints. Also, the roles of main ear photosynthesis in yield production of wheat. Hence, experiment was carried out in a split-plot factorial arrangement based on randomized complete block design in three replications during 2009-2010 and 2010-2011 seasons in the agricultural research field of Razi University. Exogenous application of IAA was used at the beginning of cell division (from anthesis till four days later) and grain filling stage (from 14 days after anthesis till four days later) and ear photosynthesis inhibiting (ear shaded) on two wheat cultivars (Phishtaz and Marvdasht). Water deficiency also applied at grain filling stage of different cultivars. The results revealed that all the growth and yield parameters such as 1000 grain weight and grain yield decreased progressively with water stress after anthesis. In control treatment grain yield of Marvdasht cultivar significantly was higher than Pishtaz cultivar. Application of water deficiency caused greater reduction in grain yield of this cultivar. These results showed that Marvdasht cultivar was more sensitive to applying of water deficiency at grain filling stage. Water deficiency caused less reduction in grain yield of Pishtaz cultivar. Exogenous application of IAA at cell division stage of grain growth caused significant increase in grain yield of cultivars. In this situation, greater increasing of grain yield was seen in Marvdasht and Pishtaz cultivars. The inhibition of ear photosynthesis reduced grain yield of two conditions. Ear photosynthesis makes a significant contribution to grain yield of bread wheat, 42% in the absence of stress and 19.6% under water deficit. Also, significant contribution to thousand grain weight of bread wheat, 36.1% in the absence of stress and 29.2% under water deficit. Exogenous application of IAA could not reduce the effect of removal ear photosynthesis treatment.

Wheat, Yield, Water deficiency, Grain filling, Indole-3-acetic acid, Ear, Photosynthesis