Studies On Tolerance And Accumulation Of Sedum Aizoon L.to Cu²⁺,Pb²⁺,Zn²⁺ Stress

We used Sedum aizoon L. as experimental material with the Nutrient solution culture experiment in green-house. Eco-physiological responses and tolerance mechanism to Cu²⁺,Pb²⁺,Zn²⁺ stress of Sedum aizoon L.are mainly studied. The change of antioxidant enzymes SOD,CAT activity,soluble suger and soluble protein's content under heavy metal stress are emphaticly discussed. Heavy metal stress on the effect of chlorophyll content, root vigor, membrane permeability and the conveyance and enrichment of heavy metals in plants are also significantly presented in the study. So we can get a better understanding of the capacity of aizoon's accumulation ,absorption and tolerance to Cu²⁺, Pb²⁺ and Zn²⁺ . At the same time a preliminary study about the ability of Sedum aizoon to withstand adversity was carried out. Supply a theoretical basis for studying the potential of soil remediation. Preliminary Results are as follows:Moderate Cu²⁺ stress don't have an obvious toxicity to the Sedum aizoon ,and have a certain advantage function on their growth, The content of chlorophyll increased when the stress Aggravated,the growth of Sedum aizoon was obviously inhibited:plant wilting,old leaves turn yellow,root turn brown,the growth of root was inhibited,the content of Chlorophyll decreased. Root vigor has an effect of "low promotion, high-suppression", Root vigor increased under the mild stress and declined under the severe stress. After incurred by Cu²⁺ stress, Sedum aizoon L. start some physiological and biochemical reactions to withstand the stress of adversity, showing the changes of Osmotica content and antioxidant enzyme activity. With the increasing Cu²⁺ concentration the accumulation of osmoregulation substances soluble sugar and proline in plants increased. SOD activity reduced with the extension of processing time. Initial stress, The activity of SOD increased with the Cu²⁺ increasing concentration ,but the enzyme activity decreased during the late stages of development, The activity of CAT in plant were activated by lower or mediate copper enrichment content of Cu²⁺ and inhibited by higher copper enrichment content;The absorption of Cu²⁺ in plant largely accumulate in roots.With the increasing in the concentration of Pb²⁺, the root morphology and root activity changed. It showed that the main root thickened, the number of root increased; the number of lateral roots increased too, lateral root length shortened; root activity increased.The content of Chlorophyll present the promotion with the low concentration and the inhibition with the high concentration.The soluble sugar content increased on the mild stress condition. The content of soluble sugar decreased With the Pb²⁺ concentration declining. The change tendency of the Proline content shows it increase first and then decrease. Antioxidant enzymes SOD and CAT under the lead stress all showed effects of "low-promotion, high-inhibition". However, all the level of SOD activity were lower than the comparison, indicating SOD is more sensitive to Pb²⁺. With the increasing concentration of heavy metals, the trends of MDA content changes are increasing in major conditions. When the concentration of Pb²⁺ is 960μmol/Ll, MDA content reduce to the comparison level. When the Pb²⁺ concentration is higher than 960μmol/L, the content of Pb²⁺ in aerial parts reaches saturation. The transportation of Pb²⁺ in plants has been hampered to protect the aerial parts from injuries, improve the plant patience to a certain extent .The majority content of Pb²⁺ remain in roots.The root system is injuried by Zn²⁺ stress, the root turn black, root volume expansion, root activity decreased significantly. The response of Chlorophyll content to zinc stress is similar to Pb²⁺. They all expressed effects of "low promotion,high-suppression". Low concentration of Zn²⁺ stress, SOD activity increased continuously with the extension of stress time. High concentrations of Zn²⁺ stress, SOD activity dropped continuously with the time extension. The activity of CAT tendency were activated first and then inhibited. With the augmentation in the concentration of Pb²⁺, the permeability of cell membrane increased. The trends of soluble sugar content change is similar to lead stress. The accumulation of Proline is similar to copper stress. Zinc that Sedum aizoon L. absorb are mostly limited to the roots. Although the concentration of Zn²⁺ in the aerial parts does not reach the standards of hyper-accumulator plants, the level of enrichment is also high.Different stresses that (heat, cold, drought) stress was carried out in this experiment .We found when the treatment temperature is higher than 45℃or lower than -1℃,it causes irreversible damage to the permeability of cell membrane. There is only a little damage to the cell membrane within the limits of temperature. The magnitude of relative conductivity changes do not keep pace with the temperature. Within the limits of temperature ,relative conductivity change relatively gentle with the temperature changes . Once the treatment temperature was close or above critical level, the relative conductivity increase sharply, And then slowly increased to a stable. The injury rates have the same trends.We also found Sedum aizoon L. has a strong drought resistance capacity in this experiment, the permanent wilting phenomenon emerge under the drought stress for 480 d.The content of water in soil is 3.97%. Slightly higher than the latter part of the temporary wilting 3.25%。...