Effect of Different Nitrogen Levels and Cytokinin Foliar Application on Yield and Yield Components of Wheat at Terminal Heat Stress Conditions in Ahwaz

Grain yield of bread wheat (Triticum aestivum L.) is reduced by heat stress، particularly when occurs in reproductive phase، in many countries worldwide، including Iran. In order to study the effects of different levels of nitrogen and cytokinin on wheat yield and yield components at normal and heat stress conditions in Khuzestan، Iran، this research was conducted at Ramin Agriculture and Natural Resources University in 2010-2011. This study was carried out in two separate factorial experiments in randomized complete block design with four replications. The first experiment was planted in a normal date and the second experiment was planted late (Terminal heat stress). In both experiments، nitrogen (N) was applied in four levels (0، 75، 150، and 225 kgha-1) and Cytokinin (Ck) sprayed in three levels (0، 50 and 100 µM). The results of both experiments (normal and stress conditions) showed that by increasing the N rate، the grain yield (5652. 1 and 3874. 7 Kg/ha respectively)، biological yield، number of spikes per m2، spikelet’s per spike، grains per spike were significantly (p<0. 01) increased. Application of Ck at normal sowing date increased the grain yield (4856. 7 kg/ha) and 1000 grain weight (41 gr) significantly (p<0. 01) and at late sowing date only increased 1000 grain weight (30. 2 gr) significantly (p<0. 01). Application of N and Ck in both experiments significantly increased grain yield (p<0. 05) and only at late sowing date increased 1000 grain weight significantly (p<0. 01). Based on our findings، application of N and Ck may lead to the amelioration of terminal heat stress effects on bread wheat in hot regions such as Ahwaz.