Study On Adaptability And Mechanism Of Heavy Metals In Ricinus Communis L.Grown In Mine Tailing

Ricinus communis L. is sorted in Euphorbiaceae and Euphorbia, annual or perennial grass. Because of the strong root system deeply in the soil, highly cold resistance and extensive adaptability, Ricinus communis L. usually is considered as an important plant of ecological and economical value.Taking Ricinus communis L. as the pot experiment material and soil contaminated with lead-zinc tailings as the substrate, a greenhouse study was conducted to observe seedling emergence and growth, physiologic and biochemical indexes and the accumulated concentrations of heavy metals of Ricinus communis L.. In order to obtain theoretical support for the tolerance mechanism to heavy metals, the potential of applying the energy plant of Ricinus communis L. to remediate contaminated soils was also discussed. The main restults were as followings:1.The heavy metal of the substrate with lead-zinc tailings played a positive role in promoting all the emergence percentage, emergence viability,survival rate of seedings and vegetative growth. In the range of setted concentration of heavy metal,the emergence percentage, emergence viability,survival rate and vegetative growth of Substrate E that the concentrations of lead and zinc remains below to1255.37,1428.00mg.kg-1was all increased and significantly higher than those in the control group. Contrarily, vegetative growth and reproductive growth were inhibited to some extent in the Substrate A (100%lead-zinc tailings).2.Concentration of heavy metal in substrates elicits opposing effects on the chlorophyll concentration, structure of chloroplasts and photosynthetic characters. The results showed that a certain concentration of heavy metal promoted the synthesis of photosynthetic pigments,while the structure of chloroplasts was normal.Wheras, the high concentration level of heavy metals lead to the decomposition of chlorophyll, decrease of chloroplasts,malformation of chloroplasts, dissolution of thylakoid lamellar as well as the number of starch grains in chloroplasts of leaves increased.Similarily,eavy metal could stimulate the net photosynthetic rate (Pn). The experimental results showed that the daily variation of Pn increased firstly and then decreased with the increment of adding proportion on slag.Pn in the Substrates B,C,D and E were higher than those in the control group G by11.37%,18.45,%,32.94%and21.96%, respectively. There was no obvious difference in the transpiration rate(Tr) but showed promoting effect on Tr.3.Heavy metals in substrate elicits opposing effects on the antioxidase system.A certain range of setted concentration of heavy metals promoted enzyme activity,in other words,the contents of SOD,POD and CAT of leaves went up when the concentration level of heavy metal was relatively low, but declined when the concentration level was high. The activity of enzyme gradually decreased as the concentrations of lead and zinc was higher than1364.17,2121.OOmg.kg-1.Treatment D was the critical point that the content of MDA rose firstly and then declined.4. The different volume of heavy metal in substrates showed obvious difference to the contents of N,P,K,Ca and Mg in plant..Some differences existed among different substrates, for example, the accumulation of N and Mg in treatment groups was below than the control group.A significant positive correlation were observed between the accumulation of P and K in castors and the concentrations of heavy metal in substrate.The accumulation of P and K was higher than control groups.Ca accumulation declined when the concentration level of heavy metals was relatively low5.There was difference among the accumulation and transformation of heavy metal in different substrates. In the stage of vegetative growth,the absorption and accumulation amounts of heavy metal was in the order of root>stem>leaf>fruit while there was certain difference among the transformation of different elements.In the later stage of growth,the constant aggravation of toxicity,leaf lost green,freshweight descended result in its die.The results of growth development,physiological and biochemical characteristics, accumulation and transformation characteristics showed that Castors was proved to possess good metal-tolerance ability and is not the hyperaccumulator of Pb and Zn, but have good application prospects in remediation of lead-zinc contaminated soils because of the high resistance of biomass.