Fig. 1

a Morphological characteristics i.e., the mortality rate (%), average plant growth (cm), and biomass yield (%), of cotton seedlings exposed to salt stress and treated with melatonin. The error bars show the standard deviation. The black marks show the least significant differences between the treatments and CK. The blue marks show the least significant differences between CK+ and the treatments. * = significant and NS = non-significant differences when p-value is 0.05. b Phenotypes of the seedlings exposed to salt stress and treated with different melatonin concentrations. Where CK = 0.8% salt stressed, B1, B2, B3, and B4 = 0.8% salt-stressed seedlings exogenously sprayed with 100 ml of 50 μM, 100 μM, 200 μM, and 500 μM melatonin solution, respectively, and CK+ = no salt treatment and no melatonin treatment