Exogenous Application of Cyclo (Leu-Pro) Enhances Drought Tolerance in Maize (Zea mays L.) by Regulating Physiological Responses, Osmotic Homeostasis, and Oxidative Defense System
Abstract
Drought stress causes considerable loss of important crops, thereby threatening global food security. The current work was designed to mitigate the harmful effects of drought stress in maize plants through cyclo (Leu-Pro) seed priming. Seeds were soaked in cyclo (Leu-Pro) (5, 10, and 20 ppm) for 12 h, and water-soaked seeds were kept as controls. Later, seeds were grown in plastic pots by adjusting field capacities (FC): 100% FC (well-watered condition) and 50% FC (drought condition). Outcomes showed that drought stress considerably reduced growth, chlorophyll pigments, and nutrient uptake. Seed priming with cyclo (Leu-Pro) increased growth and chlorophyll contents via enhanced nutrient uptake and reduced oxidative stress levels in plants under drought stress. Furthermore, cyclo (Leu-Pro) increased the endogenous nitric oxide and hydrogen sulfide levels in maize plants to mitigate oxidative stress under 50% FC. Seed priming with cyclo (Leu-Pro) improved drought tolerance associated with greater enzymatic (superoxide dismutase, peroxidase, and catalase) and non-enzymatic antioxidant (phenolic, flavonoids, and ascorbic acid), and improved osmoregulation through higher accumulation of osmolytes, such as sugars, proline, amino acids, and glycine betaine. Cyclo (Leu-Pro) mediated redox balance and osmoregulation helped in alleviating drought effects, predominantly in plants treated with a 10 ppm concentration. These findings suggested that the exogenous application of cyclo (Leu-Pro) serves as an appropriate treatment to increase the physiological and biochemical characteristics of maize under drought stress.