Modulation of antioxidant enzymes and growth traits by exogenous application of auxin and cytokinin in wheat under induced drought stress

An experiment was conducted to study the effect of phytohormones (auxin and cytokinin) in mitigation of drought stress on pairs of contrasting genotypes of wheat i.e. tolerant (DBW 110 and HI 1655) and susceptible (BW Local 1 and BW Local 2) at seedling stage under four conditions. Drought was induced by PEG 6000. It was observed that phytohormones had a significant role in mitigating stress by adjusting growth parameters, physiological parameters, reactive oxygen species level and antioxidants activity. Application of auxin and cytokinin leads to desirable changes in shoot length (2.36 and 3.26), root length (1.21 and 1.17), seedling length (2.36 and 2.74), fresh shoot weight (1.24 and 1.28), fresh root weight (1.41 and 1.21), fresh seeding weight (3.37 and 4.19), total chlorophyll (1.72 and 1.63), maximal quantum yield of photosystem II (1.51 and 1.70), stomatal conductance (1.38 and 1.19), catalase activity (4.75 and 5.68), ascorbate peroxidase activity (14.63 and 18.05) and proline content (1.37 and 1.28) and hydrogen peroxide content (1.22 and 1.31) represented in average folds as compared to control. Fresh seedling weight showed positively significant correlation with fresh shoot weight (r=1.00**), shoot length (r=1.00**), catalase (r=0.99*), ascorbate peroxidase (r=0.99*), seedling length (r=0.98*), total chlorophyll (r=0.97*) and negative and significant correlation with hydrogen peroxide (r=-1.00**) under effect of auxin whereas it showed positively significant correlation with fresh shoot weight (r=1.00*), chlorophyll b (r=0.98*), stomatal conductance (r=0.98*), maximal quantum yield of photosystem II (r=0.97*), total chlorophyll (r=0.96*), chlorophyll a (r=0.95*), fresh root weight (r=0.95*) and significant and negative correlation with hydrogen peroxide (r=-1.00*) under effect of cytokinin indicating that these are the important traits targeted by the phytohormones to mitigate the stress. Biplot analysis revealed that traits were grouped as positively correlated (all traits except H2O2) and negatively correlated (H2O2) to the drought tolerance. Study concluded that application of auxin and cytokine can minimize yield reduction of susceptible high yielding genotypes under drought stress. Further study under natural stress is required to understand the mechanism of phytohormones in mitigation of drought.