| As one of major grain crops in China, rice(Oryza.sativa L.) is prone to contain excessive content of arsenic due to its strong capacity for As absorption and special submerged cultivation method. Consequently, Arsenic can enter human body via food chain and jeopardize people’s health. Therefore, studying a technology that can lower As content in rice is important for safe production on rice paddy polluted by As. Selenium is a necessary microelement for human and animals. Se-deficiency will lead to decreased immune function of human body as well as a lot of diseases. China is a country where Se-deficiency is prevailing with 72% of its territory demonstrating Se-deficiency. To increase Se content in rice through applying Se fertilizer is one of effective measures to raise people’s Se intake. Previous studies have indicated that there is antagonism between selenium and arsenic in the organism. Selenium can effectively alleviate toxicity of heavy mental on plants. The effects of Se fertilizer application on rice growth as well as As and Se accumulation of rice were systematically studied through some pot experiments, aiming to explore the effect of exogenous selenium regulation arsenic and selenium absorption and the mechanism of Se alleviating the toxicity of arsenic to rice, and provide scientific reference and basis for safe rice production on As-polluted areas. The results are as followings:1. A pot experiment was conducted to investigate the effect of different spraying times of exogenous Se on the plant growth and As and Se accumulation in rice under As stress. The result indicated that As inhibited rice growth, and decreased the above-ground dry weight and yield of rice. Spraying Se could effectively alleviate the toxicity of As on rice, enhance rice’s photosynthesis and raise its above-ground dry weight as well as yield. Under the same condition of total amount of selenium, spraying Se for once during full heading stage increase rice grain’s Se content by 4.41-22.60 times and reduce its As content by 18.9%-40.9%,while spraying Se for twice during booting stage and heading stage increase rice grain’s Se content by 3.34-20.6 times and reduce its As content by 15.9%-23.8%. Therefore spraying Se for once at full heading stage in As- polluted rice can achieve the effect of reducing As content and increasing Se content.2. A pot experiment was conducted to study the effects of foliar application of Se alone, or Se and Si together on plant growth, yield, photosynthesis as well as As and Se absorption and accumulation in rice cultivated in different As contaminated soil. It showed that foliar application of Se and spraying Se and Si could effectively enhance the photosynthesis rate of rice and raise dry weight of stem and leaf as well as yield under the condition of As polluted. At the same time, spraying Se alone and Se+Si treatment significantly inhibited the transfer of As from stem to leaf and rice, and spraying Se+Si is better than spraying Se only. Silicon inhibited the transfer of Se to rice leaves and grains, and the content of Se in leaves and grains of Se+Si treatment were only 63.1%-77.8% and 68.6%-87.3% of Se treatment, respectively.3. The effects of selenium(0-10mg/kg) on rice growth, yield, antioxidant system, photosynthesis, As and Se uptake and accumulation in rice under As stress were investigated by applying a pot experiment. The results showed that application of Se in soil increased the resistance of rice seedlings to oxidative stress induced by arsenic, and significantly reduced the activity of SOD, POD and the content of MDA in rice seedlings. Se treatment increased the rate of photosynthesis(28.1%-60.7%) and yield(4.6%-28.3%), and the maximum value was reached at 5mg/kg Se treatment. ≥5mg/kg Se significantly inhibited the transfer of As from stem and leaves to grain under arsenic stress condition, and the content of As in rice grain reduced by 20.6%-24.9%. The content of Se in rice plants increased with the increase of selenium treatment levels. The selenium species in rice treated with Se were mostly organic selenium(43.96%-95.05%), and SeMet accounted for the main part of organic Se. The percentage of organic Se species in grain increased, whereas the ratio of inorganic Se species declined with the increase level of Se treatment, but the Se species in the stem showed the opposite trend. As treatment affected the content and species of Se in rice plant. As treatment not only improved the content of Se in the stem, leaf and grain at 10mg/kg Se treatment, but also enhanced the percentage of organic Se species in root and stem as well as reduced the ratio of Se(VI)in leaves and grains of rice treated with≥5mg/kgSe. |
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