Reactions Of 4 Greening Tree Species To PAHs Stress

With the increasing of population, the rapid development of industrialization and urbanization,excessive consumption and unreasonable utilization of resources and energy, the global worsening ecological environment has been a serious threa t to human survival and life. Polycyclic aromatic hydrocarbons(PAHs) is a kind o f persistent organic pollutants widely exists in the environment with carcinogenic, teratogenic and mutagenic. Residual PAHs reduces the soil environmental quality and pose a threat to humans through the biological enrichment. But there is lack of system knowledge about the dynamic adjustment process of rhizosphere und erPAHs stress and rhizosphere ecological system of the roots exudate affects th e dominant factor in PAHs.In this paper four kinds of changsha greening tree species (Koelreuteria p aniculata, Magnolia liliiflora, Cinnamomum camphora, Osmanthus fragrans) we re chosed as research object, pyrene was selected as representative PAHs,three treatments were selected(LO:0mg·kg-1; L1:500mg·kg-1; L2:2000 mg·kg-1),r oot exduate and root morphology were comparative analysised under pyrene str ess, responding mechanism of root exudate on pyrene stress was explored. The main research results are as follows:(1)There were vary in compound types of root exudate under different trea tments, compound types of Koelreuteria paniculata root exudate:L1 treatment (20)> L2treatment (19)> L0 treatment (15), a reduce in Magnolia liliiflora ro ot exudate:L0 treatment (35)> L1 treatment (27)> L2 treatment (14), Cinna momum camphora:L1 treatment (14)> L2 treatment (10)> L0 treatment (7), Osmanthus fragrans:L0 treatment (16)> L2 treatment (14)> L1 treatment (1 3), the chemical composition in the root exudate of four types of greening tree species under different treatment also significantly changed.(2)Total carbon (TC) content in root exudate of 4 kinds of greening tree s pecies under different treatments ranged as follows:4.86 to 28.78mg·L-1, total nitrogen (TN) content:0.98 to 7.59mg·L-1,under L0 and L1 levels TC content of Koelreuteria paniculata goldenrain were higher than the rest tree species,und er L2 level, the highest was Osmanthus fragrans. TN content of Koelreuteria p aniculatai were the highest under three different treatments.(3)With the increase of concentration of pyrene, the fresh weight and dry weight of aerial part and underground part of 4 kinds of greening tree species presented the trend of rising first and then downward. Root cap ratio of fresh weight and dry weight presented the trend of downward and then increasing, s eedling height, root volume, root length and lateral root length showed no cons istent trends.(4)Root active absorption area of four greening tree species under different treatments ranged:3.89 to 6.56m2, active absorption area ranged:2.53 to 3.43m2, ro ot active area percentage ranged:49.48% to 80.59%, scope of root phosphatase activity was:6.99-69.56nmol·g-1·FW-1·min-1. The phosphatase activity ofKoelreut eria paniculata under three kinds of treatment were the highest.