Effects Of Different Regulation Measures On Growth And Physiological Characteristics Of Rice In Copper-polluted Paddy Fields

Grain filling stage is an important stage to determine the yield and quality of rice,and the hormone content in plants plays an important role in regulating grain filling.In this study,the topsoil contaminated by copper but still planted with rice（copper content of early rice subsoil was 223 mg/kg,copper content of late rice subsoil was 235 mg/kg）was used as the material.Potted experiment of early and late rice was set.Four treatments were set for early rice:SSi,different concentrations of potassium fertilizer（K1,K2）and copper pollution control（CK）.Four treatments（SSi,K,T and CK）were applied to late rice to explore the effects and mechanisms of different regulatory measures on photosynthesis,grain filling characteristics,endogenous hormone content changes,yield and quality of rice.It provides theoretical basis for reducing copper pollution in paddy fields.The main research results are as follows:（1）Under the conditions of sulfur silicon fertilizer and leaf spraying potassium fertilizer,the toxic effect of copper on rice was slowed down,and the photosynthetic characteristics of rice sword leaves（SPAD value,leaf area index,photosynthetic potential and population growth potential）were effectively increased,thus ensuring the supply of photocontract compounds.Compared with CK,SSi,K1 and K2 treatments increased the yield by 72.24%,21.47%and 43.77%,respectively.SSi and K treatments increased the yield of late rice by 41.64%and 19.13%,respectively.SSi treatment increased the yield of early and late rice by the largest amount.（2）The addition of biochar is not conducive to the growth of rice in the cop-polluted paddy fields,and the photosynthetic characteristics of the sword leaves of rice decreased to different degrees,resulting in a decrease of 15.61%of rice yield compared with the control.（3）The application of sulfur silicon fertilizer and potassium fertilizer decreased the ABA content,increased the contents of IAA,CTK and GA3,and increased the average filling rate(G_mean),maximum filling rate(G_max)and maximum growth at filling time(W_Gmax),shortened the time to reach maximum filling(T_max),and increased the grain weight.Correlation analysis showed that A value,G_mean,G_maxand W_Gmaxwere significantly positively correlated with the contents of IAA,CTK and GA₃,while ABA content was significantly negatively correlated with them.（4）The application of sulfur and silica fertilizer and leaf spraying potassium fertilizer decreased the brown rice rate,chalkiness,chalkiness grain rate,amylose content,grain copper content and husk copper content of rice,increased the milling rice rate,milling rice rate,length to width ratio,gum consistency and protein content of rice,and improved rice quality.However,the effect of biochar treatment on rice quality was just the opposite.Correlation analysis further showed that photosynthetic characteristics（photosynthetic potential,population growth potential）and IAA,CTK and GA₃were positively correlated with yield,mwhite rice percentage and protein content in early and late rice.It was negatively correlated with grain copper content,husk copper content,brown rice percentage and amylose content,but ABA content was opposite.In conclusion,the application of sulfur silicon fertilizer and potassium fertilizer can improve the photosynthetic capacity and filling rate of rice in copper-polluted paddy fields and affect the contents of endogenous hormones IAA,CTK and GA₃,which is the key to increase rice yield and improve rice quality.The effect of sulfur silicon fertilizer combined application is the best,followed by the application of 1.5%potassium sulfate solution 7days after spiking.