Influence Of Zinc Stress On Physiological And Biochemical Characteristics In Populus × Canescens

Zinc is plant nutrient,and a toxic heavy metals to the environment.In recent years, with the development of industrial, a large number of lead-zinc mining more than the zinc levels which the plant required for normal growth, which not only cause toxicity to plants,soil and water pollution, but also enter the food chain, cause serious human health threat.Therefore, to repair the heavy metal contaminated soil utmost urgency. However,the traditional repair methods cost more investment, more time, and easily lead to secondary pollution.What's more,the previous hyperaccumulator plants often grow slowly with low biomass, used for phytoremediation is not satisfactory. Therefore, to screening a large number of high enrichment plant with fast growth capability and strong resistance has broad application prospects.The poplar (Populus×canescens) is a fast growing perennial woody plants which has important economic and ecological value. Currently found that in previous studies, the poplar have a strong accumulation of cadmium congeners with zinc (Wang Xin and Gu Yong-feng 2007), but there is quite few experimental evidence to prove the poplar have a strong accumulation of zinc. Therefore, the main purpose of this study is to clarify the effect of deficiency and enrichment of zinc on the physiological and biochemical characteristics in poplar, To explore enrichment capacity and tolerance mechanisms of poplar to zinc in hope of provide evidence to breeding zinc enrichment plant and soil pollution remediation. Take the poplar (Populus×canescens) grown in solution culture as the experimental material, we report the effects of two zinc stress conditions during low(0μmolL-1ZnSO4) and high(2000μmolL-1ZnSO4)to the photosynthetic rate,morphological, biomass indices,the accumulation amount of zinc in internal organs, the activity of enzymes of CAT,POD,SOD and the contents of MDA of poplar seedlings. Draw the following conclusions:(1)In zinc deficiency and high zinc stress,the net photosynthetic rate, the transpiration rate and stomatal conductance of poplar decreased significantly compared with controls, but the intercellular CO2 concentration in the low zinc stress increased slightly but not significant in the high zinc stress.Therefore, the decline in photosynthetic rate was non-stomatal factors.(2) In deficiency zinc stress, the fresh weight of root, leaf, stem, bark, stem diameter and leaf number of poplar were significantly decreased; Under high zinc stress, the stem fresh weight, root length, stem length and stem diameter of poplar were significantly decreased, the growth were severely disrupted. Deficiency of zinc stress also makes the green leaves turn yellow, become smaller, the number of fibrous roots significantly reduced, white short roots almost disappeared;In high zinc stress ,the leaf of poplar chlorosis ,turn gray, smaller, and a lot of gray-brown spots. The roots become dark, loss of vitality, without short root retention.(3)During the high zinc conditions, the zinc contents of roots, stems, leaves and bark of poplar were significantly increased, expressed as roots> leaves > bark> stems; In zinc deficiency conditions, the zinc contents of roots slightly higher ,in leaves and stem bark was significantly increased, while the contents in stems was extremely reduction. Prove that the poplar's roots, bark and leaves had a strong accumulation abilition to zinc but the stem was only the role of zinc transport channel, they don't have significant zinc accumulation characteristics.(4) Under zinc deficiency stress, the enzyme of CAT, POD and SOD activity of poplar's roots, stems, leaves, bark were significantly reduced, MDA content increased significantly; In the high zinc stress, The enzyme of CAT, POD, SOD activity and MDA contents of four organs were significantly increased. This prove that the poplar could timely eliminate superoxide anion produced by the high concentration of zinc in environment,then reduce the damage to the plants caused by zinc stress.To some extent, the poplar played an important role in resistance to zinc enrichment.