Effects And Mechanisms Of Organosilicon In Relieving Heavy Metal Toxicty Of Crops

With the rapid development of China's society and economy,soil pollution is becoming increasingly serious,in which cadmium?Cd?,lead?Pb?and other heavy metals are the major pollutants.Studies have shown that silicon?Si?can effectively alleviate heavy metal toxicity of crops,reduce the absorption and accumulation of heavy metals in crops,and increase crop yields.However,the effect and related mechanism of organosilicon to alleviate crop heavy metal poisoning are still unclear.In this study,we used organosilicon fertilizers and different organosilicons to conduct experiments of Cd and Pb stress mitigation on corn,wheat,and rice,respectively,to clarify the effects of organosilicon on the mitigation of heavy metal poisoning in different crops,and reveal the related mechanisms from the aspects of soil passivation and crop physiological and biochemical properties.The main results obtained are as follows:1.Field experiment showed that the application of organosilicon fertilizers promoted maize growth,increased yield,and reduced Cd content in corn by reducing the availability of soil heavy metal.Compared with CK,organosilicon fertilizers significantly increased maize plant height by 9%-16%,yield by 123%-127%,increased absorption and utilization of fertilizers N,P,and K,and increased dry weight in various parts of the maize as well as harvest coefficient.Meanwhile,compared with CK,organosilicon fertilizers significantly reduced the Cd content of shoot at the jointing stage by 40%-45%,and grain at the maturity stage by 11%-13%,and increased the p H of acidic soil by0.11-0.21 units,reducing soil exchangeable Cd by 8%-11%.2.Soil culture experiment with constant temperature and humidity showed that the addition of organosilicon fertilizers increased the p H of acid soils and decreased the p H of alkaline soils.At 90 d,fertilization caused the soil p H to decrease by 0.51 unit,while different conditioners increased soil p H by 0.06-0.38 units compared to fertilization.In addition,the organosilicon fertilizers can not only effectively increase the p H of acidic soil,but also reduce the p H of alkaline soil,and the effects were enhanced with the increasing amount of organosilicon fertilizers.3.Soil pot experiment showed that Si fertilizers effectively promoted the growth of wheat in Cd and Pb compound contaminated soil,effectively alleviated the toxic effect of Cd and Pb compound pollution in wheat in alkaline soil,and reduced human health risks caused by food intake.Compared with CK,the application of organosilicon fertilizers?OSi Fs?increased the number of tillers,spikes,and dry weight of wheat root,shoot and grain.Among them,the grain yield increased by 45%-65%.In addition,OSi Fs increased the photosynthetic rate and chlorophyll content of wheat,reduced the contents of H₂O₂and MDA,and reduced the Cd and Pb contents in wheat shoots,bran and flour.Among them,OSi Fs reduced the content in flour of Cd by 10%-17%,and Pb by 53%-74%.The calculation of health risk index?HRI?and grey correlation analysis showed that the application of Si fertilizers reduced the health risks caused by consumption of this kind of food,and the effect of organosilicon fertilizers on Cd and Pb toxicity alleviation of wheat was better than that of inorganic silicon fertilizer.4.Hydroponic experiment showed that organosilicons promoted the growth of rice plants under Cd stress,and reduced Cd transport coefficient and the accumulation of Cd in shoots by regulating the expression of Cd transporter-related genes in the roots of rice.Compared with CK,aminopropyltriethoxysilane?KH550?at 1.5 m M?KH550?1.5??and diethylenetriaminopropyltrimethoxysilane?MK?at 1.5 m M?MK?1.5??significantly increased rice shoot height and root length,rice biomass?dry weight?,and significantly enhanced leaf chlorophyll content?SPAD value?.Among them,KH550?1.5?and MK?1.5?increased dry weight of shoot by 55%and 52%,and root by 136%and 78%.In addition,KH550?1.5?and MK?1.5?reduced the Cd transport coefficient from root to shoot by 86%and 82%,and reduced the Cd accumulation in rice shoot by 73%and 62%.Although the Cd content in rice root increased,the relative expressions of Nramp1 and Os HMA3 were up-regulated,suggesting that organosilicon promoted the sequestration of Cd in the roots into vacuoles to alleviate the Cd toxicity in rice root.