Kinetin and 24-epibrassinolide - induced antioxidant responses in three wheat cultivars during drought stress in grain filling stage

The interaction of hormones plays an important role in plant equilibrium, especially, when plants encountered to environmental stresses, during both vegetative and generative stages. For this purposes, the experiment was designed based on the interaction effect of exogenous treatments of individual kinetin (Kin) and 24-epibrassinolide (24-EBL) and their dual application with two level of field capacity of 100% (control) and 50% (drought stress) from the origin of post-anthesis stage in three wheat cultivars including drought-tolerant (Pishtaz), drought-semi-tolerant (Sabalan) and drought-susceptible (Gaspard) as factorial experiment based on split plot in a randomized complete design with four replications in greenhouse condition. Then, flag leaves fresh and dry weight (FW and DW, respectively) and relative water content (RWC), abscisic acid (ABA), peroxide hydrogen (H2O2) and malondialdehyde ( MDA ) levels and enzyme activity of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalas ( CAT ) were assayed and compared at post-anthesis stage. During drought stress, FW, DW and RWC, especially in the Gaspard cultivar, decreased significantly. The ABA level increased under drought stress, especially in drought-tolerant cultivar. The 24-EBL was the most effective treatment in related to increasing of FW and DW, recovery of RWC and increment of ABA level during drought stress, especially in drought-tolerant cultivar. Drought stress significantly increased the activity of SOD, APX and CAT in Pishtaz cultivar more than Sabalan and Gaspard cultivars. In contrast, less accumulation of H2O2 and MDA was observed in drought-tolerant cultivar than both drought-semi-tolerant and drought- susceptible cultivars. Despite the fact that, EBL was the most effective treatment in related to increment of antioxidant enzymes activity, Kin and EBL combination caused the most reduction of oxidative stress traits. In conclusion, Pishtaz cultivar compared to Sabalan and Gaspard cultivars benefited from hormonal treatment for increasing of antioxidant efficiency under drought stress.