Table 2.

Roles of melatonin in waterlogging stress tolerance.

Species	Scientific Name	Waterlogging Treatment	Melatonin Treatment		Functions	References
			Concentration *	Application Form
Apple	Malus baccata	Waterlogging stress (9 d)	200 µM (foliar spraying) 600 µM (root irrigation)	Foliar spraying or root irrigation	Endogenous melatonin ▲, antioxidant enzymes ▲, chlorophyll ▲, photosynthesis ▲, aerobic respiration ▲, synthetic enzymes ▲ ROS ▼, MDA ▼, anaerobic respiration ▼, chlorosis and wilting ▼	[118]
Alfalfa	Medicago sativa	Waterlogging stress (10 d)	100 µM	Foliar spraying pretreatment	Endogenous melatonin ▲, gene expression regulation ▲, photosynthesis ▲, electroleakage ▼, MDA ▼, leaf senescence ▼, polyamine and ethylene metabolism reprogramming	[119]

▲ or▼, enhanced or decreased compared to control. ROS, reactive oxygen species; MDA, malondialdehyde. * Only those doses of exogenous melatonin that had a superior positive impact on plant tolerance against waterlogging stress have been selected.