Effects Of Silicon On Rice Growth And Arsenic Uptake

With the development of science and technology and the improvement of industrialization, environment pollution caused by heavy metals has often been reported. Arsenic is widely present in the environment as a toxic trace element. Rice unique physiological characteristics make it easier to accumulate arsenic and become one of the important ways of arsenic entry into the food chain. After eating rice,arsenic enters the human body through the food chain and poses a threat on human health. Rice is a typical siliciphilous plant, and silicon can promote the growth and high yield of rice. It has also been reported that silicon can significantly reduce the arsenic uptake in rice plants. Therefore, the study of an effective method to reduce the accumulation of arsenic in rice and the risk of food is very important. In this study, rice varieties with uptake capacity of high arsenic and low arsenic were screened by studying the difference of arsenic concentrations in different varieties of rice using greenhouse pot experiment and hydroponic experiment. The effects of two kinds of silicon fertilizer on the growth and arsenic uptake of two kinds of rice were also studied. The main conclusions are as follows:(1) There were significant differences in the yield, biomass and plant height of different rice varieties under arsenic stress. There were significant differences in nitrogen and phosphorus contents among different cultivars.And their content were decreased in this order: grain> stems and leaves> husk. The arsenic content of different rice varieties was different in arsenic stress, the distribution rules of arsenic in mature rice were as follows: root> leaf> stem> husk> grain. The content of arsenic in grains was significantly different among different rice varieties(p<0.05). Among the 11 rice cultivars tested, ZhenDao16, Wu YunJing 23, NanJing 5055 and SuXiu 9 were the rice varieties with low arsenic uptake. TaiRuiFeng 5 and HuaiDao 6 were the rice varieties with high arsenic uptake, and arsenic contents in the grains of these rice varietes was higher than 0.4 mg · kg-1 in the brown rice, which was stipulated by the World Health Organization. Therefore, we can plant the rice with low arsenic uptake in arsenic contaminated areas, to reduce arsenic accumulation in rice and reduce arsenic content in human body through the food chain.(2) Under the hydroponic experiments, sodium silicate has no significant effect on biomass of ZhenDao16, which may be due to the short processing time of rice and the small biomass in vegetative growth. The iron plaque of root can promote phosphorus sequestration. Sodium silicate can reduce the amount of iron plaque and content of phosphorus on root surface, with the most significant effect under the arsenic concentration of 10μM. Sodium silicate significantly reduced the arsenic content of roots and shoots in ZhenDao16. These results showed that the iron plaque on root surface did not enter the barrier of heavy metal arsenic into rice, but promoted the uptake of arsenic in rice.(3) In the soil culture experiment, the plant height, yield and biomass of ZhenDao 16 and TaiRuiFeng 5 were decreased under arsenic stress of 60 mg · kg-1.The effects of two kinds of silicon fertilizer on ZhenDao 16 and TaiRuiFeng 5 were different. In the soil without arsenic, the application of sodium silicate reduced the yield of ZhenDao 16 and TaiRuiFeng 5, but the silicate gel increased the yield of ZhenDao 16 and TaiRuiFeng 5. In the arsenic added soil, the two kinds of silicon fertilizer can promote the production of TaiRuiFeng 5, but reduced the yield of the ZhenDao 16. In the soil with arsenic addition, the two kinds of silicon fertilizer had little effect on the biomass of both rice varieties, and the nitrogen content in each organ did not show a significant difference, but increased the phosphorus content in each organ to a certain extent. Both sodium silicate and silica gel could significantly reduce the arsenic content in various organs of rice, but the effect of slow release silicon fertilizer, silica gel, was better than that of sodium silicate. For the two kinds of rice, the effect of low-arsenic uptake cultivar ZhenDao 16 was higher than that of high arsenic uptake type TaiRuiFeng5.