Investigation Of Manganese, Nitrogen Regulation On Cadmium Accumulation In Rice Plants

Cadmium(Cd),an important toxic heavy metal,has been polluting more and more paddy fields due to uncontrolled application of fertilizers containing high level of Cd,sewage irrigation and mining establishments,and ultimately enters into food chains causing potential threat to human body.Excess Cd in soils can also result in poor growth of crop plants,and reduce crop productivity.Therefore,much attention has been taken to the problem on Cd pollution which should be urgently solved with consideration of both Cd concentration in food such as rice and crop productivity.Investigation of manganese regulation on rice seedling stage growth and cadmium accumulation in rice plantsThe present study investigated the effects of manganese on rice growth,and cadmium accumulation and its distribution between shoots and roots under Cd stress with hydroponics.The results showed that Cd toxicity to rice plant was markedly alleviated by normal manganese level with higher plant height and root length,enhanced content of chlorophyll a,chlorophyll b, carotenoid,and improved antioxidant systems compared to those in low manganese treatment, while high manganese reinforced the Cd toxicity because of much higher concentration of manganese in nutrient solution causing severe toxicity to rice plants.Cd accumulation in rice shoots increased,while that in rice roots decreased with the increase of manganese in solution. Based on the results,the feasibility to control Cd accumulation in rice plants by application of Mn fertilizer and its forms to be used were discussed.Investigation of using manganese to control cadmium accumulation in rice plants and rice grainsMnSO₄ and EDTA.Na₂Mn used as manganese fertilizers were applied to soils or sprayed on rice plants to study the effects of manganese species and fertilizer methods on cadmium accumulation in rice plants with soil culture systems.The results showed manganese fertilizer application pose hardly adverse effects on plant growth and rice grain yield.EDTA.Na₂Mn applied to soil significantly reduced the Cd accumulation in rice roots,shoots and rice grain,and Cd concentration in white rice of both rice genotypes was much lower than 0.2 mg/kg,the national maximum limits for Cd concentration in foods.However,MnSO₄ applied to soil or spraying with MnSO₄ or EDTA.Na₂Mn on rice plants lead to markedly enhanced Cd accumulation in rice plants including rice grain compared with the control.Based on our results,it might be hypothesized that applied to soil with those manganese fertilizers which could keep the ferrous species long time in soils maybe a new promising way to control Cd accumulation in rice grain in rice production.Investigation of nitrogen regulation on rice growth and cadmium accumulation in rice plantsA hydroponics experiment was conducted to study the effects of nitrogen on rice growth and cadmium accumulation between shoots and roots under cadmium stress.The results showed that cadmium toxicity to rice plant was markedly alleviated by the increase of the nitrogen level with higher plant height,root length,leaf length and leaf width,more tiller number,enhanced content of chlorophyll a,chlorophyll b,carotenoid,however,high nitrogen treatment reinforced the cadmium toxicity compared to those in normal nitrogen treatment in a certain extent.The results also showed that cadmium accumulation in rice shoots decreased,while that in rice roots increased with the increase of nitrogen in solution.Based on the results,the feasibility to control cadmium accumulation in rice plants and increase rice yield by application of nitrogen fertilizer were discussed.