EFFECTS OF MELATONIN ON PHYSIO-BIOCHEMICAL AND IONIC STRESS MARKERS IN MAIZE AT SEEDLING STAGE UNDER SALT STRESS

Oxidative stress due to salinity creates a challenging situation for seed germination and early seedling establishment in maize. Over than normal production of reactive oxygen species (ROS) leaves cataclysmic effects on the physiology of plants when subjected to saline environment. Melatonin is versatile stress mitigating organic molecule reported to have significant potential for scavenging ROS. The present study was conducted with the aim to study the effects of different concentrations of melatonin viz., control, 500, 1000 & 1500 µM on the physiological and bio-chemical stress markers in the six maize genotypes viz., MMRI-Yellow, NCEV-1530-9, YH-1898, Composite, SB-9617 and FH-949.The study was planned in sand culture (pot study) using CRD with factorial arrangement. The results of the present study demonstrated that melatonin priming in all the concentrations viz., 500,1000 and 1500µM significantly enhanced the germination percentage (by 14.0 , 25.0 and 27 %), chlorophyll a (23.3, 43.3 & 40.0 %), chlorophyll b contents (by 29.2, 50.0 & 50.0 %), total soluble sugar-TSS (by 20.0, 31.5 & 40.4 %), total soluble protein-TSP (by 10.0, 15.5 & 20.5%), chlorophyll stability index-CSI (by 15.0, 20.3 & 25.6%), membrane stability index-MSI (13.3, 25.7 & 26.6%), relative water contents-RWC (13.7, 23.3 & 24.0%), phenolic contents-TP (14.8, 24.3 & 26.8 %), proline contents-Pro (23.0, 35.2 & 37.7%), superoxide dismutase-SOD (by 25.5, 41.0 & 45.0 %), per-oxidase-POD (by 17.8, 25.1 & 24.7%), catalase-CAT (by 37.7, 51.5 & 54.3%) and reduced concentrations of H2O2 (by19.3, 26.5 & 30.1 %), malondialdehyde-MDA contents (by 15.1, 22.4 & 22.3%) and electrolyte leakage-EL (by 12.4, 18.0 & 16.5 %), compared to un-primed seed treatment. Interestingly the higher concentrations of melatonin were statistically produced the same effects. The genotype SB-9617outperformed, with respect to higher accumulation of photo-pigments, TSS, TSP and TP with improved of membrane stability, relative water contents and enhanced activities of the anti-oxidant enzymes (SOD, POD and CAT) showed reduced lipid per-oxidation and electrolyte. In PCA-bi-plot, PC1 and PC2 contributed maximally i.e. 90.9 and 3.7% to explain the total variations i.e 94.6 %. Additionally, SB-9617 with melatonin priming@ 1000µM proved the best to mitigate adverse effects of salt stress at germination and early seedling growth stage via cross taking with physiological and bio-chemical stress markers.