The Responses Of Germination And Growth Of Castor Bean(Ricinus Communis L.)to Heavy Metal Stress

The responses of germination and seedling growth of castor bean(Ricinus communis L.)to heavy metal stress was studied under different heavy metals(Cu,Zn,Cd)and different concentrations(0,30,60,120 mg/L).The results are following:1.The effect of heavy metals on germination of castor beanThe percentage of water absorption of castor seeds treated with different concentrations of Cu2+ was higher than CK.The percentage of water uptake of castor seeds treated with the high concentration(120 mg/L)Zn2+ and Cd2+ was higher than CK.The water absorption rate of castor seeds increased first and decreased then and increased final,the water uptake rate of castor seed was no significant difference from 0 to 36 hour.When the treatment time was 48 h,the water absorption rate of the different treatments were obvious difference.With the prolonging of the treatment time,the water absorption rate of the seeds treated with high heavy metals concentration was higher than CK.The germination rate of castor seeds treated with different Cu2+ concentrations was not significantly different with CK.The germination rate of castor seeds treated with Zn2+ was significantly higher than that the control treatment,and the germination rate of castor seeds treated with Cd2+ was decreased.Heavy metals inhibit the decomposition rate of crude fat and affect the changes of soluble protein content in seeds.The content of soluble sugar of castor seeds treated with Zn2+ and Cd2+and Cu2+ increased with the heavy metal concentration increased.The soluble sugar content decreased with the increase of heavy metal concentration.2.Effects of Heavy Metals on Growth and Development of Castor SeedlingsWith the increase of heavy metal concentration,the leaf area of castor bean decreased,the dry weight of stem and root and whole plant and SPAD increased first and then decreased.The plant height of castor bean treated with Cu2+ and Zn2+ increased first and then decreased with the increase of heavy metal concentration,and the plant height treated with Cd2+ decreased.During the beginning of castor bean growth,the soluble protein content and POD increased with the increase of heavy metal concentration.When the accumulation of heavy metals increased in the plant,the soluble protein content decreased and POD increased.SPAD,soluble protein,SOD,POD and MDA physiological indicators showed that the 120 mg/L concentration had the greatest capacity to inhibit the castor bean growth.3.Effects of Different Heavy Metals on Nutrient Uptake and Utilization and Accumulation of Heavy Metals in Castor PlantsThe uptake of nitrogen by castor bean root,stem and leaf decreased with the increase of heavy metal concentration.The accumulation of phosphorus in stem and leaf decreased and increased first and then decreased in root with the accumulation of heavy metal.The potassium absorbed by the stem was lower than the control,and the accumulated potassium in the leaves was greater than the control.The contents of Cu,Zn and Cd in the parts of castor bean were root>stem>leaves.The contents of Cu,Zn and Cd in the castor bean were Zn>Cd>Cu at the same heavy metal concentration.In this study,it was found that the high concentration of heavy metals Cu,Zn and Cd inhibited the seed germination rate,water absorption rate and the content of the storage material during the germination process,and effect on the growth and development of castor bean.Three heavy metals had different inhibitory capacity to effect the growth of castor bean,while Cu,Zn and Cd at concentrations of 120 mg/L did not lead castor bean to die,indicating that castor was resistant to high concentrations of heavy metals.