Abstract
Cadmium (Cd), a life threatening hazardous heavy metal is abundant in nature. Cd amounts are greater in leaves than other plant parts, and it shows considerable effects on photosynthesis. Nitric oxide (NO), a free radical present in living organisms, is now known as an important signaling molecule playing various physiological processes in plants. In this study, the possible ameliorative effect of NO on photosynthesis was examined on pea seedlings grown under Cd stress. Results showed that chlorophyll, net photosynthetic rate, transpiration rate, stomatal conductance, photochemical efficiency of Photosystem II and Photosystem I decreased, and Fo and non-photochemical parameters for PSII and PSI significantly increased due to Cd stress. This suggests that Cd affects the photochemistry efficiency at both the PSII and PSI levels. Nitric oxide supplementation through SNP ameliorated Cd stress by enhancing all the above mentioned parameters but causing a reduction in the Fo, and non-photochemical parameters of PSII and PSI in pea plants. These data indicate that the exogenous application of NO was useful in mitigating Cd-induced damage to photosynthesis in pea seedling.
Highlights
Heavy metals including Cd occur naturally in soils in trace amounts
Ratios of Chl a/b and Chl/Carotenoid increased by 6.00% and 24.00%, respectively, at 50 μM Cd, and 14.00% and 46.00%, respectively, at the 200 μM Cd treatment compared to controls (Figs. 1C and 1D)
Multiple linear regression analysis (MLR) revealed that seedlings in presence of Cd resulted in a reduction of chlorophyll a, chlorophyll b, total chlorophyll and carotenoid concentrations
Summary
Heavy metals including Cd occur naturally in soils in trace amounts. Anthropogenic activities have led to Cd contamination of agricultural lands [1]. Cd is taken up from soil and transported to all parts of plant, as a result become potential hazard for both plant and animals [2]. Cd causes (1) inhibition of many physiological processes in plants like nitrogen assimilation, mineral nutrition, photosynthesis, respiration, transpiration, and carbohydrate metabolism (2) increases in chlorosis, wilting, necrotic lesions, and oxidative stress, and induction of senescence, all of which reduce biomass production [3,4]. Cd stress has been associated with reactive oxygen species (ROS) generation, including superoxide ions (O2−), hydroxyl radicals (HO) and hydrogen peroxide (H2O2) [5,6].
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