Effects Of Different Control Measures On "Source-Sink-Flow",Yield And Quality Of Rice At Filling Stage In Copper-Polluted Paddy Fields

Crop groups or individuals can generally achieve high yield only when they have sufficient source,large sink,and smooth flow.This study is based on the "source sink flow" theory of crop yield formation,and investigates the effects and mechanisms of different regulatory measures on the "source sink flow" and yield and quality of rice during the filling period in copper polluted rice fields.This study conducted a pot experiment in the greenhouse of the Science and Technology Park of Jiangxi Agricultural University in2021.The tested varieties were super rice Wufengyou 286 for early rice and conventional rice Fenghuazhan for late rice.The experiment was divided into two seasons: early and late rice.The soil used for the early rice experiment was the topsoil of Zhangfang Township,Xiaogang Town,Dongxiang Copper Mine,Jiangxi Province,which was contaminated but still being planted with rice.The copper content was 223 mg · kg-1,and four treatments were set up: copper pollution control(CK),sulfur and sodium silicate combination application(SSi),and additional foliar spraying of 0.75% and 1.5% potassium sulfate solution(K1,K2)7 days before heading;The copper concentration in the late rice test soil was 235 mg · kg-1,and four treatments were set up: copper pollution control group(CK),sulfur and sodium silicate combination application(SSi),additional foliar spraying of potassium sulfate solution(K,the same as early rice K2 treatment)7 days before heading,and biochar(T).The aim of this experiment is to investigate the effects of different regulatory measures on the photosynthetic characteristics of rice leaves during the filling stage,the transport and accumulation of assimilates in stems and leaves(source),the characteristics of vascular bundles in the ear neck(flow),the transport and accumulation of assimilates in grains(sink),and yield and quality in copper polluted rice fields,providing data support and theoretical basis for actual agricultural production.The main conclusions are as follows:(1)Under the control of combined application of sulfur silicon fertilizer and foliar spraying of 1.5% concentrated potassium sulfate solution,the growth and development of rice in copper polluted paddy fields were effectively promoted,and various related indicators of "source sink flow" were significantly improved.Among them,the leaf area index(source),number of vascular bundles and surface area(flow),and number of endosperm cells(sink)increased by 31.85% to 58.25%,32.81% to 48.98%,and 27.55% to40.45% compared to the copper polluted control group,respectively.At the same time,the yield and quality of rice were improved.Under the application of sulfur silicon fertilizer,the yield increased by 41.64% to 72.24%,the protein content increased by 10.53% to16.16%,and the grain copper content decreased by 38.00% to 45.59%;Under the foliar spraying of 1.5% potassium sulfate,the yield increased by 19.13% to 43.77%,and the copper content in grains decreased by 30.00% to 38.24%.(2)Under the control of foliar spraying with 0.75% potassium sulfate solution,the vascular bundle area(flow)of rice in copper polluted rice fields increased by 14.06% to16.33% compared to the blank control group,but there was no significant impact on the number(flow)of vascular bundles and the related indicators of "source" and "sink".The yield and quality of rice were not significantly improved compared to the control group under its regulation.(3)Under the regulation of acidic biochar(p H 5.1),the growth and development of rice in copper contaminated rice fields were inhibited,and various indicators of "source sink flow" showed varying degrees of decline compared to the copper contaminated control group.This also had a negative impact on rice yield and quality.Under its regulation,rice yield decreased by 28.16%,and grain Cu content increased by 13.79%.(4)The improvement of "source" and "sink" by the combination application of sulfur silicon fertilizer and foliar spraying of 1.5% potassium sulfate solution is mainly through promoting the activity of metabolic enzymes related to the sucrose starch pathway,and under the catalysis of sucrose synthase(SS),soluble starch synthase(SSS),adenosine diphosphate glucose pyrophosphorylase(AGPase)and starch branching enzyme(SBE),promoting the transformation of sucrose into starch,improving the output and transport of stem and sheath substances,Improve the thousand grain weight and seed setting rate,thereby increasing rice yield.In summary,by analyzing and comparing the data related to the "source sink flow" and yield and quality of early and late rice in 2021,it was found that the optimal control measures for rice growth and development in copper polluted rice fields were the combination application of sulfur silicon fertilizer and foliar spraying of 1.5% concentrated potassium sulfate solution.