Effects of exogenously applied plant growth regulators on the physiology and anti-oxidant activity of wheat under water deficit condition

An experiment was conducted to know the effect of plant growth regulators, Thidiazuron; 0.01 µL L⁻¹, Paclobutrazol; 30 µL L⁻¹, Ascorbic acid; 100 µL L⁻¹, on wheat genotypes under osmotic stress imposed with PEG 6000 and water-deficit stress in pots. Under osmotic stress with PEG6000, the total chlorophyll content and ethylene evolution were estimated from wheat seedling, and in pot experiment, detailed physiological studies were performed at different growth stages (pre-anthesis, anthesis and post anthesis) of wheat under water deficit stress and irrigated condition. Study revealed that the level of ethylene increased while the content of chlorophyll decreased under osmotic stress condition. Moreover, the higher level of ethylene and chlorophyll content were observed in C306 followed by in HD2987 as compared to HD2888 and HD2733 under control as well as in osmotic stress conditions. However, application of plant growth regulators (PGRs) led to the down-regulation of ethylene evolution from osmotic stressed wheat seedling while the chlorophyll content was improved across the wheat genotypes. Further, in pot experiment, PGRs application on water deficit stressed plants led to the improvement in ascorbic acid content and ascorbate peroxidase (APX) activity while the abscisic acid and thiobarbituric acid reactive substances (TBARS) content goes down in comparison to water deficit stress plants without PGRs application. Findings of the study indicated that due to simultaneous application of PGRs plant developed a sense of lower stress level thus lesser ethylene evolution and lipid peroxidation (TBARS content) was observed. Further PGRs application helped in maintenance of chlorophyll and ascorbic acid content with higher APX activity under water deficit condition indicating better tolerance level. The results of this study provide a synergetic effect of PGRs for abiotic stress tolerance.