ABSTRACT: Drought stress is a major limiting factor in crop production at arid and semi- arid areas. It is well known, application of plant growth regulators and nutrients could be useful to improving plant tolerance to water stress condition. In this research, the effects of these type of compounds as foliar application was investigated on enzyme activity and tolerance in terminal drought stress at Pishgam wheat cultivar. A field experiment in Ajabshir region in 2016-2017 was designed as a randomized complete block design (RCBD) with eight treatments in three replications. The results of ANOVA clarified that treatments had significant (P≤1%) effects on wheat morphological traits including harvest index, number of spikes per m2, number of fertile tiller and seed proteins and were significant on TKW and peduncle length at 5% probability. The effect of compounds foliar application on moisture traits of flag leaf such as relative water content (RWC), Relative water deficit (RWD), membrane stability index and flag leaf protein were significant at 1% probability. In terms of physiological traits at flag leaf such as a-chlorophyll, b-chlorophyll, total chlorophyll, malondialdehyde and catalase, guaiacol peroxidase and ascorbate peroxidase enzymes were significant at 1% probability. Also ANOVA results showed that there is not significant between foliar applications vs. control in biological yield, grain and straw yield. But yield differences were considerable value between urea, salicylic acid and folic acid foliar applications vs. control. Foliar application of urea could increase biological, grain and straw yield, 3219 kg.ha-1 (19.8%), 2704 kg.ha-1 (42.4%), 512 kg.ha-1 (5.4%) respectively. This could be explained by increasing number of fertile tillers (29.4%) and decreasing number of non-fertile tillers (36.6%) in plant and therefore existence of nice source to remobilization of photosynthesis materials and consequently increasing harvest index (20.5%) in urea treatment
