Cadmium stress consolation in melatonin supplemented Cucumis sativus through modulation of antioxidative defense system

Abstract

Current studies elucidate the metal stress attenuation potential of melatonin in <em>Cucumis sativus</em> seedlings growing in cadmium contaminated conditions. Melatonin is an indoleamine molecule, capable of ameliorating environmental stresses and regulate plant growth. Seeds of <em>C. sativus</em> were immersed in different levels of melatonin and grown under cadmium stress for 15 days. Cadmium stress reduced seed germination, growth, biomass production, gas exchange capacity, stomatal conductance and chlorophyll (Chl) content in <em>C. sativus</em> seedlings. The increased level of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) caused oxidative stress in <em>C. sativus</em> plants under cadmium stress. Melatonin application emphatically revamped germination, shoot, and plant biomass production. The melatonin pretreatment aggrandized plant length, root length, and expression of stress related genes (CsHA2, CsHA3, CsHA4, CsHA8 and CsHA9) along with amplification in activity of superoxide dismutase (SOD), nitrate reductase (NR), and ascorbate peroxidase (AP) helping in modulation of cadmium stress in <em>C. sativus</em> seedlings. The improved activity of antioxidant scavengerswas ascribed to the reduced level of H₂O₂and MDA in plants under stress. Furthermore, conjugated increase of photosynthetic activity, indole acetic acid contents, and glutathione contents was observed in melatonin treated seedlings in a dose-responsive manner. The present study elicits the metal stress attenuating potential of melatonin by regulating metabolic activities and growth of <em>C. sativus </em>under cadmium stress.