Study Of Heavy Metals Lead And Cadmium On The Accumulation And Tolerance Of Bamboos

The different treatment concentrations of Pb²⁺and Cd²⁺ to pollute phyllostachys aureosulcata,phyllostachys nigra,phyllostachys vivax,P.praecox. C.d. Chu and P.vivax McClure in the paper under potted plant experiment .Five species were used to study Pb²⁺and Cd²⁺ on absorption and accumulation,allocation and migration in the different organs,phyllost- achys nigra, and phyllostachys aureosulcata were selected based on that because the absorpt- ion and accumulation of lead and cadmium was in the large.To elucidate deeply and systematically the toxieity and tolerance mechanisms of the selected two bamboo species to heavy metals, this investigation was carried out to study effcets of single Pb and Cd on membrane permeability, lipid peroxidation and antioxidant enzymes systems,as well as a preliminary comparison to resistance of two bamboo species.The main results were sununarized as follows:1. The result showed that,accumulation of phyllostachys aureosulcata,phyllostachys nigra ,phyllostachys vivax,P.praecox. C.d. Chu and P.vivax McClure to Pb and Cd were most in roots,and the following accumulated organs were in whip, stems and leaves,respectively, which is the common discipline of different bamboo species under the single Pb, Cd stress.Different bamboo species have different capacities of absorption and accumulation under the same heavy metal stress. Under Pb stress , the capacity of uptake and accumulation in five bamboo species is in the order: P.vivax McClure> phyllostachys nigra > phyllostachys aureosulcata>P.praecox. C.d. Chu > phyllostachys vivax;under Cd stress, the order is: P.vivax Mc Clure>phyllostachy saureosulcata>P.praecox .C.d. Chu> phyllostachys nigra>phyllostach ys vivax.2. The same kind of heavy metal show some differences in allocation and migration in different banboos. Pb²⁺ or Cd²⁺ absorbed from the soil in five bamboo species was mainly accumulated in roots and whip, only a very small part of ions moved upward to the stem and lsaf. The capacity of migration of Pb²⁺ in five species of bamboo from the root to stems and leaves is in the order: phyllostachys aureosulcata>phyllostachys vivax>P.vivax McClure> phyllostachys nigra >P.praecox. C.d. Chu; under Cd stress, the order is: phyllostachys nigra > P.praecox. C.d. Chu >phyllostachys aureosulcata >P.vivax McClure >phyllostachys vivax.3. Studying the effects of Pb and Cd on lipid peroxidation and antioxidant enzymes systems of two kinds of bamboos indicated that single Pb and Cd made the membrane leakage enlarge, membrane lipid peroxidation enhance. Cell plasma membrane damage stronger with the increasing concentration of heavy metals, showing a significant increasing in relative conductivity and time effect; accumulation of MDA increased with the inereasing of treatment concentration and the prolonging stress days.4.It was significantly negative correlation between all the indexes of chlorophyll and the concentration of Pb stress during the time of treatments,and chlorophyll(a),chlorophyll(t) content were inhibited seriously by different concentration of Cd.The net photosynthetic rate,and stomatal conductance decreased with the increasing stress concentration,but the intercellular CO2 concentration inereased. The decreasing of net photosynthetic rate of under heavy metal stress,was caused by nonstomatal limitation;single Pb and Cd stress has a significant influence on diurnal variation of photosynthesis of phyllostachys aureosulcata and phyllostachys nigra, generally speaking,the two kinds of bamboo were up to the maximum value of net photosynthetic rate (Pn)at 12 o,olock, as the concentration increased, the maximum value of Pn moved forward at about 10 o,olock, the maximum of Gs and the minimum of Ci corresponded to the Pn .5. The antioxidant enzyme activities showed the general trend under single Pb and Cd stress in phyllostachys aureosulcata and phyllostachys nigra:as the Pb and Cd treatment concentration increased, the antiqxidant enzymes activity increased in the same period;as the stress time prolonged, the antiqxidant enzymes activity were induced increasing first, then declining under the same concentration .According to comprehensive evaluation, it showed that, phyllostachys aureosulcata is more tolerant than phyllostachys nigra under Pb,and phyllostachys nigra is more tolerant than phyllostachys aureosulcata.