Effect of paclobutrazol on the amount of redistribution of assimilates to the grain of three cultivars of wheat (Triticum aestivum L.) under heat tension conditions

In order to investigate the effect of plant growth regulatory of paclobutrazol on the amount of redistribution of assimilates to the grain of three cultivars of wheat under favorable and terminal heat tension conditions two independent experiments were conducted as split plots in a randomized complete blocks design and with four replications in Dezful area in 2013-2014 cropping year. The first experiment ncluding the cultivation of wheat cultivars (Star, VeerNac and Chamran) in recommended date (November) and in order to coincide phenological stages of plant growth with terminal heat tension after pollination, planting date in another experiment was considered on the first of February. In each experiment, four levels of paclobutrazol included zero, 50, 100 and 150 mg per liter as main plots and three cultivars of bread wheat included Star, VeerNac and Chamran were considered as sub plots. Results showed that paclobutrazol consumption significantly increased the amount of redistribution of food storage and current photosynthesis of wheat cultivars in both favorable and terminal heat tension conditions. Heat tension, reduced the amount of redistribution and the amount of current photosynthesis about 12 and 31 percentage, respectively. Average share of the redistribution of wheat cultivars in heat tension conditions compared to favorable conditions, 17 percentage increased. The highest and lowest amount of share of the redistribution in heat tension conditions compared to favorable conditions was dedicated to the late maturity cultivar Star and earlymaturity VeerNac, respectively. In this research, the positive effect of using paclobutrazol on the gradient of the changes the amount of grain yield in terminal heat conditions was more than favorable conditions, so that the average increase in grain yield of paclobutrazol applying treatments in studied cultivars of wheat compared to the control treatment (non-use of paclobutrazol), in favorable conditions, was about 17 percentage and in season terminal heat tension conditions, about 23 percentage.