Accumulation Varietion Of Hg,As,Sb,Tl In Different Coix Cultivars

Screening crop varieties with low accumulation of heavy metals is an important measure for the safe production of agricultural products in moderately and lightly polluted soil.In this study,soil with different heavy metal pollution levels in Lan Muchang Hg,As,Sb,Tl mining area of Xingren,Guizhou province were selected for field experiments to study the heavy metal accumulation characteristics,growth and physiological and biochemical characteristics of seven Coix lacryma-jobi cultivars.The main results obtained are as follows:(1)different varieties of coix lachryma-jobi parts most of Hg,As and Sb content:root>leaf>stem>grain,Tl content:root>stem>leaf>grain.The contents of Hg,As,Sb and Tl in coix seeds were the highest in the heavily polluted areas.Hg content in grains of all coix lachryma-jobi cultivars in the heavily polluted area exceeded the food safety standard,and As content in grains of two cultivars exceeded the food safety standard.Meanwhile,Tl content in grains of two cultivars was high,which might be risky.The content of Hg and As in seeds and stems of coix lachryma-jobi in lightly and moderately polluted areas did not exceed the standard.(2)The average enrichment coefficients of Hg,As,Sb and Tl in coix roots were0.30,0.08,0.09 and 0.63,respectively,which were all less than 1.Coix had weak absorption capacity of As and Sb,but relatively strong absorption capacity of Tl.The mean transport coefficients of Hg,As,Sb and Tl in coix seeds were 0.0068,0.0162,0.0232 and 0.0155,respectively,which were less than 0.03,indicating that coix was weak in transporting heavy metals to seeds.(3)Under heavy metal stress,plant height of Coix lachryma-jobi in severely polluted area decreased by 23.58%on average.The average biomass per plant in the lightly,moderately and severely polluted areas was 20.30,20.44 and 16.22g,respectively,and showed a trend of first increasing and then decreasing.The average yield of Coix lacryma-jobi in lightly,moderately and severely polluted areas was 3992.01,2183.78 and 2140.04kg·hm~2,respectively,which significantly decreased.The yield of Coix No.3 remained high in different polluted areas,and coix No.3 was selected as the optimal variety with low accumulation based on clustering analysis of heavy metal content in grains.(4)Chlorophyll in coix lachryma-jobi leaves decreased with the increase of pollution.But Coix No.3 showed an upward trend and showed high tolerance.With the increase of pollution degree,SOD,POD and CAT activities in leaves and roots increased first and then decreased.The SOD and CAT activities in leaves were higher than those in roots,indicating that leaves could maintain the activities of these two enzymes better than roots and protect organisms from injury.Coix No.3 maintained high antioxidant enzyme activity under different pollution levels,and showed better resistance to heavy metal stress.In conclusion,Coix No.3 is an optimal variety with low accumulation of heavy metals,and has high yield and strong tolerance to heavy metals.It can be used in the safe utilization of lightly polluted soils in Hg,As,Sb and Tl to realize the safe production of agricultural products.