Effects Of As Oxidizing Bacteria D14 On Physiological Status And Organizational Structure Of Three Poplar Clones Under As Stress

Poplar, one of the most adaptable species and the most common tree species in afforestation, is widely distributed in the world. It has multiple advantages, such as well-adapted, easy to grow, fast-growing and strong resistance, specially, can be used as model woody plant to study resistance to heavy metals. In this study, three kinds of poplar, the Zhong Qian 2, LH05-143, xiaoye poplar, are taken as research materials to study the changes of physiological indicators and organizational structure under the conditions of heavy metal As stress and As-oxidizing bacteria D14.(1) Observating the growing status of the three poplar species treated by heavy metal As, we can find that not only leaves were wrinkled and yellow, leaf margin shriveled; but also roots turn black, and the amount of root growth and the number of new roots reduced. And these are heavy metal stress symptoms. However, As- oxidizing bacteria D14 is helpful in easing these stress symptoms;(2)Measuring the plant height and groung diameter indicated that growth from high to low was xiaoye poplar, LH05-143, ZhongQian2. Volume growth and growth speed of plant height can be decreased under the heavy metal stress, while As-oxidizing bacteria D14 can relieve the stress symptoms and play a protective role;(3) Studying the accumulation of As during the growth period showed that accumulation amount of root is larger than that of above ground. Whereas, As-oxidizing bacteria D14 can promote accumulation of As;(4) Determinating physiological character under the heavy metal stress suggested that MDA content, Pro content, soluble protein content, SOD activity, POD activity of the roots and shoot changed compared with the control group. Whereas, As-oxidizing bacteria D14 can relieve the stress symptoms and play a protective role;(5) By observing microstructure of xiaoye poplar leaves and roots under the heavy metal stress, we can find that palisade tissue grew interspace, cell arrangement looser, spongy tissue arrangement larger, even microtubules deformated in the leaves; similarly, root cortical cells appear deformation, dissolution, which resulted in resulting in gaps cortical cells;(6) By observing ultrastructure of xiaoye poplar leaves and roots under the heavy metal stress, we can find that starch grains content reduced, starch grains smaller, the chloroplast thylakoid expanded, Lamellar spaces become larger, small transparent chamber appears; the number of osmiophilics is increased, cells comes into plasmolysisings and lysising when stress aggravated.As the As stress increased, the number of mitochondria gradually reduced, and its structure has been damaged too.