Chitosan Enhances Drought Tolerance in Maize (Zea mays L.) by Promoting Growth and Chlorophyll Content While Reducing Hydrogen Peroxide Levels

Drought is one of the major constraints for maize (Zea mays L.) cultivation at the global level, as maize is sensitive to drought. To elucidate the impact of chitosan (CS) on improving drought tolerance in maize, the morphological and biochemical features of a drought-stressed maize variety (CAVARI 3696) at the germination and seedling stages were analyzed. The experiments performed at both stages were comprised of four different treatments in triplicate, viz., control (C), drought (D), drought with 50 ppm chitosan (D+50 CS) and 50 ppm chitosan only (50 CS). At the germination stage, drought stress significantly declined seed germination percentage and the growth and biomass of seedlings, while CS supplementation under drought enhanced germination and growth significantly. In the seedling stage, drought-stressed maize plants exhibited a significant reduction in chlorophyll contents (both Chl a and Chl b) but elevation in H2O2 buildup and lipid peroxidation measured as malondialdehyde (MDA) level. Drought stress also enhanced proline accumulation and improved catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX) enzyme activities in maize plants. However, chitosan raised chlorophyll levels and suppressed H₂O₂, MDA, and proline content in maize plants under drought stress. Moreover, CS supplementation reduced the activities of the antioxidant enzymes under drought. These results suggest that chitosan can be used to improve the growth performance of maize under drought through enhancement in defense responses against the buildup of reactive oxygen species and associated oxidative injury.