Study On Physiology And Mechanism Of Resistance In Three Chenopodiaceae Plants To Pb(Ⅱ) Stress

In recent decades, with the development of industry, the lead is used more and more, as a result of artificial active like excess lead mine exploration and the lead is dispersed into environment, the restoration of lead contamination become more important. The phytoremediation has much merits than any other methods, it is the main way to restore environment which lead contaminated. So the selection of lead resistant plants become a research focus. Salsola passerina Bunge,Kochia scoparia (L.)Schrad. and Chenopodium album L. at different Pb(Ⅱ) treatments ( 0, 50, 150, 300, 600, 800, 1000 mg/L)are conducted through the comparison ofseed germination, seedling growth, antioxidase activity and photosynthesis characters, then finding the resistant one and studying the resistance mechanism. The results are summarized as follows:(1) The effects of Pb(Ⅱ) on the germination percentage,germination energy and germination index of S. passerina Bunge and K. scoparia (L.)Schrad. are not significant (P>0.05) when Pb(Ⅱ) concentrations are 50mg/L and 150mg/L, but it is significant (P<0.05) on C.album L. once Pb(Ⅱ)concentration is up to 150mg/L. Although higher Pb(Ⅱ) concentrations (>300mg/L) inhibit the germination of the three plants,the effect on K. scoparia (L.)Schrad. and C. album L. is stronger;The vigor index of seeds of three plants are significant from control, except that of S. passerina Bunge at 50mg/L Pb(Ⅱ);The effects on radicle and plumule elongation are not significant when Pb(Ⅱ) concentration is 50mg/L. As the concentration increasing, the inhibition on the elongation of radicle and plumule of three plants become stronger, but the effect on K. scoparia (L.)Schrad. and C. album L. is stronger than S. passerina Bunge. The seedling of K. scoparia (L.)Schrad. and C. album L. died at 300mg/L and 600mg/L Pb(Ⅱ) respectively. The seedling of S. passerina Bunge still alive even at 1000mg/L, although it grows slowly.(2)When Pb(Ⅱ) concentration is under 150mg/L,the effects on the root and shoot growth of three plants are not significant(P>0.05). The root and shoot growth of K. scoparia (L.)Schrad. and C. album L. are restrained significantly at 300mg/L and 600mg/L respectively, while the root and shoot growth of S. passerina Bunge are restrained and still alive at 800mg/L Pb(Ⅱ). Different concentrations of Pb(Ⅱ) bate the lateral roots,but the extent of inhibition is not the same. The number of lateral roots of K. scoparia (L.)Schrad. and C. album L. decrease quickly also at 300mg/L and 600mg/L respectively. Once the Pb(Ⅱ) are 800mg/L above, S. passerina Bunge are restrained significantly(P<0.01), but the whole root is not hurt. With the concentrations of Pb(Ⅱ) increasing, the fresh weight of three plants are all inhibited, it indicates that Pb(Ⅱ) has heavy toxicity.(3)After treatments of different concentrations of Pb(Ⅱ), the MDA content of three plants are all increased. The MDA content of C. album L. is increased obviously at 300mg/L Pb(Ⅱ), so does K. scoparia (L.)Schrad. when Pb(Ⅱ) concentration is 600mg/L. the MDA content of S.passerina Bunge goes up slower than C. album L. and K. scoparia (L.)Schrad .once the concentration of Pb(Ⅱ) is higher than 600mg/L. At the lower Pb(Ⅱ)concentrations (≤300mg/L), the activity of POD and SOD of three plants are all boost up. When Pb(Ⅱ)concentration is higher than 300mg/L, the POD and SOD activity of C. album L. decrease. The POD and SOD activity of K. scoparia (L.)Schrad. are reduced at 600mg/L. With the concentration increasing, the antioxidase activity of C. album L. and K. scoparia (L.)Schrad. are destroyed, but the POD and SOD activity of S.passerina Bunge are still mount up, it shows that S.passerina Bunge resistances to Pb(Ⅱ). The Chlorophyll content of three plants is all decreased, and the Chlorophyll a is slow down fast.(4)To sum up , comparing with C. album L. and K. scoparia (L.)Schrad., S.passerina Bunge is more resistant to Pb(Ⅱ). Although the treatment of higher concentration (1000mg/L) has effect on S.passerina Bunge, it can still alive, the resistance mechanism of S.passerina Bunge to Pb(Ⅱ) stress is formed, which safeguarded its growth and reproduction. This mechanism is made up of as followings: Firstly, S.passerina Bunge can absorb Pb(Ⅱ), besides this,it translates Pb(Ⅱ)from root to the stem ,and the TFs is 1.3;Secondly, mass of Pb(Ⅱ) is intercepted in root and accumulated in cytoderms, so this reduces the transportation and toxicity of Pb(Ⅱ)in plants;Thirdly, there mostly existed in less activate extractable- Pb(Ⅱ)forms, less dissociative Pb(Ⅱ)in plant, so this enhances the resistance of the plant to Pb(Ⅱ)stress.