Protective Effect (Safener) of Melatonin on Vigna Radiata L. Seedlings in the Presence of the Fungicide Copper Oxychloride

Abstract

Melatonin (N-acetyl-5-methoxytriptamine) is a novel plant regulatory molecule currently under study. Its role as a biostimulator and protector against abiotic and biotic stressors, through the regulation of the redox network and change in the expression of many elements of primary and secondary metabolism, is of great interest. The possible protective effect of melatonin in mungbean seedlings, previously primed seed treated with the fungicide copper oxychloride, was studied. The effect of melatonin and fungicide in growth of seedlings and photosynthetic pigments, leakage membranes, lipid peroxidation, antioxidant activity, and phytomelatonin content was studied. Also, the effect of exogenous melatonin on endogenous plant hormones indoleacetic acid, gibberellins, cytokinins, abscisic acid, salicylic acid, and jasmonic acid levels, in the absence and presence of fungicide, was analyzed. Melatonin improved growth of roots and aerial parts in the presence of fungicide; chlorophyll and carotenoid contents were protected by melatonin in the presence of melatonin and in melatonin-fungicide co-treatments. Membrane damage due to fungicide was lessened by melatonin. The hormonal profile (auxin, gibberellins, cytokinins, abscisic acid, ethylene precursor, salicylic acid, and jasmonic acid) in roots and leaves was greatly affected by copper fungicide and melatonin treatments. In general, an increasing in plant tolerance response has been detected, proposing melatonin as a natural safener molecule of plants in the presence of copper fungicide.