| Two kinds of Trichosanthes kirilowii Maxim.were taken as the experiment materials to clarify the root exudates of Trichosanthes kirilowii have an effect on the growth and the micro ecology of rhizosphere soil.Trichosanthes kirilowii seedlings were watered with different concentrations(30,20,10 ml/plant)of root exudates under Al stress(300 μmol/L and 800μmol/L).We mainly study on the available nutrient,effects of microorganisms enzyme activities of rhizosphere soil,the growth characteristics,photosynthetic characteristics,antioxidant enzyme activity and the functional groups of root cell wall of Trichosanthes kirilowii.The results were summarized as follows:1.A1 stress could inhibit available nutrients,enzyme activities and microorganisms of micro ecology of rhizosphere soil.When we studied on the effects of root exudates under Al stress in micro ecology of rhizosphere soil of 2 varieties of Trichosanthes kirilowii,the results showed that low concentrations of root exudates(30 and 20 ml/plant)could increase the content of soil available potassium,alkaline hydrolysis nitrogen,available phosphorus,enhancethe activity of soil catalase,invertase,phosphatase,rise the number of bacteria,actinomycetes and fungi,but high concentration of root exudates(10 ml/plant)could inhibit the development of soil micro ecology.The suitable concentrations of root exudates of Trichosanthes kirilowiihas a great influence on Al stress,it can alleviate Al stress,especially in the micro ecology of rhizosphere.The optimal concentration of root exudates to alleviate Trichosanthes kirilowii is 20 mL/plant.2.A1 stress inhibits the growth of Trichosanthes kirilowii,and the biomassreduced significantly.The height increment,stem diameter increment,root length,stem fresh weight/dry weight,root fresh weight/dry weight of Trichosanthes kirilowii significantly reduced during the treatment of Al stress.It could be recovered after root exudates were applied,especially for the roots.However,with the increasing of concentration of root exudates,each index showed a trend of rising and then decreasing.3.Results showed that there were-OH,-NH,C-H,C=0,C=C,-CH2,C-N,N-H and other functional groups in the cell wall of root system.The functional groups of root cell wall showed different absorption peaks because of Al3+,functional characteristic peaks of aromatic substances of Al treated groups were less than CK.Among the low Al treatment groups,absorption peaks of 20 mL/plant was similar to CK.Thus the root exudates can protect the components of Trichosanthes kirilowii root cell.In addition,-OH,-NH,C=0,C=C,-CH2(Benzene skeleton)functional groups played an important role in neutralizing Al toxicity or chelating Al3+.4.After the treatment of Al3+,ch1 a,chl b content,chlorophyll fluorescence andCAT,POD,SOD of Trichosanthes kirilowii showed a downward trend,but MDA,initial fluorescence(FO)presented opposite trend.The indexes of two kinds of Trichosanthes kirilowii had different changes and sensitivity,indicating the difference between two kinds of Trichosanthes kirilowii in Al tolerance.After adding moderate concentration of root exudates,the content of chl a,chl b content and fluorescence parameters value,CAT,POD,SOD and other antioxidant enzymes activity were enhanced.Above all,a low concentration of root secretion can alleviate the harm of Al3+,but high concentration of root secretion do harm for Trichosanthes kirilowii,20 ml/plant is the optimal concentration of root exudates to relieve Al stress.Henceforth,finding out the influence mechanism of root exudates on Trichosanthes kirilowii in red soil area can lay the foundation for the popularization and application of Trichosanthes kirilowii. |
