Table 3.

Protective role of melatonin in various crops against different abiotic stresses.

Crop	Stress Condition	Concentration	Functions	Reference
Arabidopsis	Heat	1000 μM	Improved seed germination under heat stress	[100]
Apple	Drought	100 µM	Reduced ABA activity and radical scavenging	[101]
Apple	Waterlogging	200 μM	Reduced chlorosis and wilting of the seedlings	[102]
Barley	Senescence	1 mM	Boosted chlorophyll content	[103]
Brassica napus L.	Drought	0.05 mmol/L	Increased the overall growth indices of brassica seedlings	[104]
Bermuda grass	Cold	100 μM	Induced photosynthetic activity under cold stress	[105]
Cucumber	Salinity	100 μM	Overall growth	[95]
Cucumber	Cinnamic acid	10 μM	Rescued cucumber seedlings from Cinnamic acid stress and increased the allocation of dry weight in roots.	[106]
Eggplant	Cadmium stress	150 μmol/L	Enriched photosynthetic activity	[107]
Faba bean	Salinity	500 μM	Enriched photosynthetic activity and mineral accumulation	[108]
Grapes	Water deficient	200 μmol/L	Amended antioxidative enzymes activity	[94]
Maize	Drought	100 μmol/L	Photosynthesis and growth	[109]
Melon	Cold	200 μM	Improved proline and ascorbic acid content	[110]
Medicago sativa	Drought	10 μM	regulation of nitro-oxidative and osmoprotective homeostasis	[111]
Malus hupehensis	Salinity	0.1 mM	Improved photosynthetic activity and better plant growth	[112]
Malus hupehensis	Alkaline	5 µM	Significantly induced the tolerance against alkaline stress by increasing the antioxidant activity and biosynthesis of polyamines	[113]
Perennial ryegrass	High temperature	20 μM	Regulate abscisic acid and cytokinin biosynthesis	[97]
Potato	Salinity	100 µM	Better chlorophyll content, antioxidant activities and water content	[114]
Pisum sativum L.	Oxidative stress	50 μM	Reduced O2•− accumulation in leaf tissues and preservation of photosynthetic pigments	[115]
Rice	Salinity	20 μM	Delay leaf senescence and cell death in rice	[116]
Red cabbage	Heavy metal	10 μM	Improved seed germination and reduced the toxic effect of metal on the seedling.	[117]
Soybean	Multiple stress	100 µM	Boost and maintain the overall plant growth	[54]
Soybean	Aluminum stress	50 μM	Enhanced root growth and reduced aluminum toxicity	[118]
Sunflower	Salt	15 μM	Regulate root growth and hypocotyl elongation under salt stress	[119]
Tomato	Cold and salinity	100 μM	Improved photosynthesis and regulation of photosynthetic electron transport	[120,121]
Tomato	Heat and salinity	100 μM	Induced antioxidant enzymes activity and better photosynthetic performance	[122]
Tomato	Acid rain	100 μM	Enhanced tolerance against simulated acid rain and increased the photosynthetic activity	[123]
Tea	Cold	100 μM	Triggered photosynthetic and antioxidant enzymes activities	[62]
Watermelon	Salinity	150 μM	Redox homeostasis and improved photosynthetic activity	[124]
Watermelon	Vanadium stress	0.1 μM	Lower the concentration of vanadium in leaf, stem and better photosynthetic and antioxidants activity	[125]
Watermelon	Cold	150 μM and 1.5 μM	Alleviate cold stress by inducing long-distance signaling in the untreated tissue.	[126]
Wheat	Drought and nano-ZnO	500 μM and 1 mM	Augmented seedling percentage, growth, and antioxidant enzymes activities.	[59,127]
Wheat	Cadmium stress	50 mM	Reduce the level of hydrogen peroxide which increases the wheat plants growth	[128]