Effect of nitrogen fertilizer and cytokinin application on grain yield and physiological traits of wheat (Triticum aestivum L. cv. Chamran) under terminal heat stress condition

To study effects of different levels of nitrogen fertilizer and cytokinin on some physiological traits of wheat cv. Chamran under normal and post anthesis heat stress conditions, this experiment was conducted at Ramin Agriculture and Natural Resources University, Ahvaz, Iran, in 2012-2013 growing season. The experiment was carried out in two separate factorial experiments using randomized complete block design with four replications.The first experiment was planted in normal date of sowing (05 December 2012) and the second experiment was planted late (20 January 2013) to expose the experimental treatments to terminal heat stress. In both experiments, nitrogen (N) was applied at four levels (0, 75, 150, and 225 kg.ha-1) and cytokinin (Ck) at three levels (0, 50 and 100 µmol). Results showed that intraction effect of sowing date× nitrogen× cytokinin on prolin content and SPAD value, intraction effects of nitrogen × cytokinin and sowing date × nitrogen on FLAD (Flag Leaf Area Duration), stomatal conductance and grain yield was significant. The highest grain yield was obtained from application of 150 kg.ha-1 nitrogen and 100 µmol cytokinin, however, it was not significantly different from 225 kg.ha-1 nitrogen and 100 µmol cytokinin and 150 kg.ha-1 nitrogen and 50 µmol cytokinin. It was concluded that with increasing application levels of nitrogen and cytokinin the negative effects of terminal heat stress could be mitigated.