Selenium application reduces cadmium uptake in tomato (Lycopersicum esculentum Mill.) by modulating growth, nutrient uptake, gas exchange, root exudates and antioxidant profile

In the recent past, the application of trace elements/micronutrients has gained a considerable attention to mitigate harmful impacts of cadmium (Cd) and other heavy metals. In current study we investigated the effects of selenium (Se) in tomato (Lycopersicum esculentum Mill.) for mitigating Cd toxicity. Different applications of Se i.e., 2.0, 4.0 and 6.0 mu M were employed under 20.0 mu M Cd Stress. A significant (p <= 0.001) decrease in physiological, nutrient uptake and plant growth parameters was observed under Cd stress. A decrease of 34% in root length, 21% in shoot length, 40% in shoot fresh weight, 31% in root fresh weight, 24% in shoot dry weight and 20% in root dry weight as compared to control under Cd stress was recorded. Higher levels of antioxidants (enzymatic, non-enzymatic) indicated a higher production of oxidative stress indicators. An increase in SOD (34%), POD (65%), CAT (58%) and proline (81%) was recorded in plants treated with Cd as compared to control (Cd non treated ones). The MDA and H2O2 contents in Cd-treated plants likewise exhibited a significant increase. An augmentation of 23% in Chl A/B ratio, 39% in carotenoids, 50% in transpiration rate and 28% in net photosynthesis was recorded as compared to control under Se application. Plants recovery from Cd stress was evident after application of Se. Results indicated a decrease of 18 and 15% in MDA and H2O2 contents respectively, due to Se application. The crux of the present investigation revealed that Se application mitigated Cd stress in tomato cultivars used in this study. Tomato var. Nagina proved to be more Cd stress tolerant with lower up take of Cd to aerial parts than Roma. It is concluded from the outcomes of this study that Se improved Cd toxicity tolerance in tomato in terms of its low uptake, enhanced growth, better nutrient uptake, improved photosynthetic and antioxidant attributes. This will pave the futuristic path for exploration of the underlying molecular mechanism for Cd toxicity tolerance with Se application in tomato.