Long‐term exogenous application of melatonin delays drought‐induced leaf senescence in apple

TLDR

Melatonin’s effect on drought tolerance suggests new agricultural uses. The study examined whether long‑term exogenous melatonin improves drought tolerance in ‘Hanfu’ apple. Melatonin was applied long‑term to apple trees, and its effects on oxidative stress, photosynthesis, PSII photochemistry, and antioxidant defenses were evaluated. Melatonin reduced oxidative stress, delayed leaf senescence, lowered chlorophyll degradation, suppressed SAG12 and PAO expression, preserved photosynthesis and PSII function, and decreased hydrogen peroxide by boosting antioxidant enzymes and the ascorbate–glutathione cycle.

Abstract

Abstract To examine the potential roles of melatonin in drought tolerance, we tested the effects of its long‐term exogenous application on ‘Hanfu’ apple ( Malus domestica Borkh.). When 100 μ m melatonin was added to soils under drought conditions, the resultant oxidative stress was eased and leaf senescence was delayed. This molecule significantly reduced chlorophyll degradation and suppressed the up‐regulation of senescence‐associated gene 12 ( SAG 12 ) and pheophorbide a oxygenase ( PAO ). Such treatment also alleviated the inhibition of photosynthesis brought on by drought stress. We also investigated quenching and the efficiency of Photosystem II ( PSII ) photochemistry under dark and light conditions and found that melatonin helped to maintain better function of PSII under drought. The addition of melatonin also controlled the burst of hydrogen peroxide, possibly through direct scavenging and by enhancing the activities of antioxidative enzymes and the capacity of the ascorbate–glutathione cycle. Thus, understanding this effect of melatonin on drought tolerance introduces new possibilities to use this compound for agricultural purposes.