Effects Of Complex Pollution Of LAS/CTAB And Cd²⁺ On The Growth Of Chinese Sweetgum (Liquidambar Formosana Hance) Seedlings

In this thesis, the author investigated single and combined stress of pollution on the growth of one-year old Chinese sweetgum seedlings, including anionic surfactant linear alkylbenzenesulfonate sodium (LAS), cationic surfactant cetyltrimethylammonium bromide (CTAB) and heavy metal Cd2+. Pot planted experiments were used to measure the physiological and biochemical indicators of leaves at different growth stages of seedlings. The main results could be describle as follow:(1) In the condition of only Cd2+ pollution, it could stimulate the growth of chinese sweetgum seedlings and increase biomass, leaf area when the Cd2+ concentration in the soil resched 50mg/kg; all above-mentioned indicators were higher than those of the control. While the added Cd2+ concentration reached 100mg/kg, the growth of seedlings was severely inhibited, representing stunted plant with smaller leaf area, less biomass, lower content of chlorophyll and higher content of Malondialdehyde (MDA) of leaves.(2) In the condition of only LAS pollution, lower concentrations of LAS (0.1～1g/kg) could promote the growth of chinese sweetgum seedlings. It was harmful to seedlings while LAS concentration exceeded 1g/kg, the toxicity was extremely serious at the level of 4g/kg. In the condition of only CTAB contamination, when the added CTAB concentration in the soil was among 0.1g/kg～0.5g/kg, it could promote seedlings growth. However it was harmful to seedlings growth when the CTAB concentration reached 0.5g/kg～2g/kg, and seedlings growth could be severely inhibited at the level of 4g/kg. Under the condition of single stress, total chlorophyll content showed a downward trend with increasing LAS concentration; chlorophyll a, carotenoids increased firstly and then decreased with the increase of LAS concentration, and similar situation happened to SOD and CAT activity. But MDA content showed an increasing trend. Single CTAB stress significantly reduced leaf chlorophyll content compared with that of the control; SOD and CAT activity of leaves have shown that first-increase and then downward trend. The permeability of cell membrane in general tended to increase with the increase of CTAB concentration.(3) With incrseasing concentration of added combined Cd2+-LAS or Cd2+-CTAB respectively, total seedlings biomass increased firstly and then decreased. In the condition of Cd2+-LAS combined stress, chlorophyll content of seedlings leaves was remarkable influenced. When the added Cd concentration reached 50mg/kg and 100mg/kg, chlorophyll content increased firstly and then decreased with the increasing of LAS concentration. Similar situation happened to SOD, CAT activity. When CTAB concentration was 0.5g/kg, lg/kg SOD activity reached the peak value. At the same level of above described Cd2+ coucentration, the comblined pollution of Cd+ and CTAB caused extremely significant effect on seedling leaf chlorophyll a and carotenoid contents. With the increase of CTAB concentration, the chlorophyll content increased firstly and then decreased.(4) Compared with that in the fast-growing stage, total chlorophyll content dropped significantly at the end stage of growth stage. Moreover SOD and POD activities of at the end of growing stage were lower than those in the fast growing stage due to a long period of stress; MDA accumulation quantify of leaves increased over time.