Studies On The Effects Of ABA And BR On Cadmium Accumulation And Its Mechanism In Plants

Abscisic acid?ABA?and epibrassinolide?eBL,a highly active form of brassinosteroid?are plant growth regulators that regulate the process of plant growth and development.ABA and eBL promote plant tolerances to different stresses,including high temperature,low temperature,drought,salinity and heavy metal.In the present study,mung bean,Vicia sativa,soybean,wheat,and corn were used as plant materials to study the effects of exogenous spraying of 10?M abscisic acid?ABA?and 0.1?M epibrassinolide?eBL?on the growth,uptake and accumulation of Cd in the plants under low,medium,and high concentrations of Cd stress.In addition,the effects of ABA and eBL on physiological characteristics such as activities of APX,POD,CAT and SOD,contents of malondialdehyde?MDA?,proline,and chlorophyll in Vicia sativa under low and high concentrations of Cd stress were measured.The main results are as follows.1.Our results showed that the Cd tolerance and accumulation of the five plants were markedly different,and trending as corn>Vicia sativa?soybean?wheat>mung bean.Corn could grow normally under 1300?M Cd stress,but mung bean could only grow under 300?M Cd.Foliar spraying ABA and eBL significantly promoted the root growth of all the five plants,and increased the growth parameters of the main root length,lateral roots,root fresh weight,and dry weight of the plants under varying degrees of Cd stress.2.The Cd contents and accumulations in the plants increased with the increases of Cd treatment concentrations.Exogenous applications of ABA and eBL either reduced or increased the contents and accumulations of Cd in the stems and leaves and roots of plants.When compared with the Cd treatment alone,the treatments with 200?M Cd+ABA and 500?M Cd+ABA significantly reduced?p<0.05?the Cd contents in the stems and leaves of Vicia sativa seedlings by 22.28%and 14.09%,respectively.However,the treatments with 800?M Cd+ABA and 800?M Cd+eBL significantly increased Cd contents of in the stems and leaves?p<0.05?by 18.75%and 29.65%,and the contents reached up 103.78 mg·kg^-11 and 113.32mg·kg^-1,respectively.Our results also revealed the different sensitivity of different plants to ABA and eBL subjected to different Cd concentrations.In addition,when compared with Cd treatment alone,200?M Cd+eBL,500?M Cd+eBL,and 800?M Cd+eBL treatments increased the Cd extraction in soybean stems and leaves by 22.08%,1.13%,and 8.65%,respectively.This result indicated that exogenous applications of ABA and eBL increased the Cd extraction in the plants and improved the phytoremediation of Cd-contaminated soil using plants.3.The Cd treatment induced the increases in APX,CAT,and POD activities in plant stems and leaves and roots.When compared with Cd treatment alone,the foliar spraying ABA and eBL reduced the Cd-induced increases in CAT and APX activities in stems and leaves and roots of Vicia sativa seedlings.800?M Cd+eBL treatment reduced CAT activity and APX activity in the stems and leaves by 60.04%and 47.90%,respectively.Exogenous spray of ABA and eBL further increased POD activity in the stems and leaves and roots of Vicia sativa seedlings.Under 200?M Cd stress,ABA and eBL treatments increased the POD activity in the stems and leaves by 13.38%,27.20%,respectively,and the POD activity in the roots by 44.81%and 49.77%,respectively.Whereas,the SOD activity showed no significant change.4.The MDA and proline contents in the stems and leaves and roots of Vicia sativa seedlings increased with the increase in Cd concentration.Exogenous spray of ABA and eBL reduced the MDA contents and thus alleviated membrane lipid peroxidation of Vicia sativa seedlings subjected to Cd treatment.Exogenous spray of ABA and eBL reduced the proline content under low concentration Cd treatment,but further increased the proline content under high concentration Cd treatments.Exogenous spray of ABA and eBL increased the chlorophyll content and thus improved the photosynthetic capacity of Vicia sativa leaves.