The Mechanism Of Salicylic Acid Regulating Aluminum Stress In Trichosathes Kirilowii Maxim

Aluminum (Al) toxicity is one of the principal factors limiting crop production in south acid soils which is keeping serious because pesticide and chemical fertilizers were used without moderate by people. Now it is very important to find an economic, convenient and effective way to alleviate Al toxicity and to improve plant tolerance to aluminum, and it also have become hot spots in plant adverse circumstance research. In our study, Trichosathes kirilowii Maxim. were selected as material, cultured in solution which was treated by salicylic acid and Al in turn. The first, we should know the tolerance to Al of plant, which by determined the root vigor, plasma membrane permeability, activities of antioxidant enzymes named peroxidase (GPX), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidation (GPX), superoxide dismutase (SOD) and their isozyme electrophoresis, hydrogen peroxide content, relative aluminum content. The second, we have two ways of SA addition, one is sprinkle and the other one is adding SA to the nutrient solution. In the sprinkle treatments, these indexes were determined which contained the biomass liveweight, the activities of antioxidant enzymes, the contents of hydrogen peroxide and malonaldehyde in root and leaves. The chlorophyll content and Chlorophyll fluorescence parameters were important because sprinkle SA come into contact with leaves directly. Changes of elements uptaking and transporting, the concentration of MDA and Antioxidants, three enzyme active in the degree of lignification contained GPX, CAD and PAL were investigated in the treatment of adding SA to the nutrient solution. The results were summarized as followings:(1) The results of effects of acid aluminum stress on Root growth and aluminum accumulation of Trichosathes kirilowii Maxim. as follow:With the increasing of Al3+concentration, the activities of CAT and APX increased but the activities GPX and SOD decreased; most of the antioxidant enzymes had several electrophoretic bands, and the depths of colour in electrophoretic bands in line with antioxidant enzymes; plasma membrane permeability had no significant difference; root vigor increased remarkably. Determining relative content of aluminum had the same result by comparing with that of Morin staining. More aluminum accumulated in the cells of root hair than that in closely arranging cells. Antioxidant enzymes system and aluminum accumulation mechanism play important role in resisting Al toxicity for the growth of T. kirilowii.(2) The results of Effects of exogenous Salicylic acid on Antioxidase activity and Chlorophyll Fluorescence Parameters in Trichosathes kirilowii Maxim. under aluminum stress were as follow:with the treatment of Al, activities of SOD, CAT, APX, the contents of H2O2and MDA increased significantly; maximal photochemical efficiency of photosystem Ⅱ (Fv/Fm), maximum fluorescence (Fm), minimal fluorescence (Fo) and the chlorophyll contents, especially the chlorophyll a, decreased remarkably. We found that exogenous SA significantly reduced the contents of H2O2and MDA, activities of antioxidant enzymes which induced by Al stress. The chlorophyll contents and all the Chlorophyll fluorescence parameters also closed to the normal level by sprinkling of the exogenous SA. Besides these,10μmol/L SA promote leaves growth which were expressed by leaf area and shoot fresh weight. There is no promotion to plants with independent SA. Exogenous SA application enhanced Al tolerance in Trichosathes kirilowii Maxim seedlings, alleviated the oxidative stress and the damage of PSII center induced by Al stress.The results of salicylic acid involved in the regulation of nutrient elements uptake and the degree of lignification in Trichosathes kirilowii Maxim. under Al stress as follow:Al exposed decreased the K content and inhibited the Mg, Na and Ca transported from root to shoot. However, the exogenous SA (10μmol/L/50μmol/L) significantly ameliorated the absorbed dose lower of Mg, Ca and K caused by excess Al in plant. The MDA content and AsA, GSH concentration increased dramatically under Al expose, however, application SA partly inhibited Al-induced the membrane permeability damage and the increasing of antioxidants, make MDA, AsA and GSH contents decrease. The root growth was inhibited by excess Al, the root lengh and root fresh weight shorter and lighter than the contrast. When added SA to Al treatment, we found that the plant root growth recovered partly. The application SA decreased the activities of CAD, PAL, GPX which related to lignin compose compare with plant in Al treatment, so that root growing well. SA alone have no good effect to plant growth, that may be due to it destroy the balance of oxidation level. These results suggest that exogenous SA may involve in the regulation of nutrient balance, oxidative stress and the degree of lignification.