Alterations in antioxidative machinery and growth parameters upon application of nitric oxide donor that reduces detrimental effects of cadmium in rice seedlings with increasing days of growth

Abstract

Finding its way into the agricultural lands through various sources Cadmium (Cd) has been proved to be deleterious in plant systems. Cd-induced oxidative stress tampers with both plant's physiology and biochemistry. Nitric oxide (NO) is a key signaling molecule in plant stress response and plays a significant role in many regulatory pathways of plant development. This study investigates the effect on rice seedlings grown under 50 µM Cd/SNP alone or in combination in the growth medium, on roots and shoots of rice cv. HUR 3022 at 1, 4, and 7 days of growth. Plants treated with Cd alone showed diminished growth, decreased length and weight, lower cell viability and less chlorophyll. Application of equimolar quantity of SNP to cadmium-stressed rice within the growth medium repressed Cd-uptake and reversed the Cd-induced detrimental effects. Rice plants treated with only Cd showed high oxidative stress. Specific activity of antioxidant enzymes such as guaiacol peroxidase, ascorbate peroxidase and glutathione reductase were increased. Antioxidants like glutathione and ascorbate had lower levels in cadmium treated plants. A high amount of reactive oxygen species were generated in cadmium treated plants which were supported by the histochemical studies for - hydrogen peroxide and superoxide anion. Application of SNP in rice plants under cadmium-stress in the growth medium mitigated the Cd-induced oxidative stress by elevating the levels of antioxidants and reducing the amount of reactive oxygen species produced. These results were supported by reduced specific activity of oxidative enzymes. The results indicate that NO when supplemented exogenously, diminishes the deleterious effects of Cd in rice plants. Our study presents report from the early days of plant development i.e., 1,4,7 days of growth because physiological and biochemical changes occurring during these early developmental days may provide significant insights into rice plant's adaptation strategy towards any perceived stress. © 2020 SAAB