Exogenous Application of Tyrosine Mitigated the Adversities of Drought Stress in Maize Seedlings through Modulation of Photosynthetic Performance and Antioxidants Defense Systems

Scarcity of water is a major challenge to global food security, because productivity of food crops has significantly declined. However, the protective role of tyrosine in alleviating the adversities of drought stress is not obviously explored in cereal crops.

Therefore; current experiment was conducted to assess the potential of tyrosine concentrations (0, 50, 100, 150 and 200 mg L^− 1) on maize seedlings under drought stress (40% water holding capacity-Ck-D) and 80% water holding capacity (CK-W) was considered as well-water condition.

Results revealed that foliar application of various concentrations of tyrosine under drought stress significantly (p ≤ 0.05) increased growth attributes (shoot length, shoot dry weight, root length and root dry weight, total seedling biomass, leaf area), leaf chlorophyll pigments, leaf relative water content (RWC), net photosynthetic rate, transpiration rate, stomatal conductance, accumulations of organic osmolytes (soluble protein, proline, total soluble sugar, free amino acid) as compared to control (CK-D). Moreover; drought stress significantly (p < 0.05) augmented H₂O₂, malonaldehyde (MDA) contents and electrolytes leakage as compared to CK-W. However, 200 mg L^− 1 tyrosine application decreased 56.58% H₂O₂, 117.5% MDA contents and 42.96% electrolyte leakage with increasing 40.82% superoxide dismutase, 40.48%, peroxidase, and 49.32% ascorbate peroxidase and 33.02% catalase activities under drought stress.

Overall, it was concluded that foliar application of 200 mg L^− 1 tyrosine was found to be the most effective to alleviate negative effect of drought stress in maize through decreased damaging effect of reactive oxygen species (ROS) and enhanced enzymatic antioxidant activities and accumulation of organic osmolytes. Current findings suggest that exogenous application of tyrosine is a potential strategy for successful cultivation of maize in drought prone area.