Analysis of factors of growth stimulation by aluminum in roots of tea plants

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In this study, stimulatory effect of aluminum (Al) on the growth of roots of tea plants were studied. Follows are summary of the results:1.The growth of rooted cuttings, cultured tea cells and seedlings of tea plants were stimulated by Al, irrespective of phosphate levels.2.Lignin content, wall-bound phenolics contents were reduced by Al. Key enzyme of phenolic metabolism, phenylalanine-ammonia lyase (PAL) activity, and peroxidase (PO) activity were determined. PAL activity of roots of rooted cuttings and seedlings were clearly decreased by Al. The activity of soluble, ionically-bound, and covalently-bound PO also decreased by Al in all samples.3.Effects of Al on lipid peroxidation, H_2O_2 contents, and on the activities of antioxidant enzymes (catalase : CAT, ascorbic acid peroxidase : APX and superoxide dismutase : SOD) were examined. Lipid peroxidation and H_2O_2 contents were decreased by Al treatment in tea rooted cuttings, tea seedlings and cultured tea cells. The activities of CAT, APX and SOD were increased by Al treatment in tea plants.4.3-AT, an inhibitor of CAT, inhibited the activity of CAT completely, but H_2O_2 contents were not affected. It is considered that the reduction of H_2O_2 contents in Al treatment is carried out by APX and/or low molecular antioxidative substances. Effect of NaCl was also examined in tea cells. Increase of lipid peroxidation and the increase of H_2O_2 contents were observed.5.From the results in the reduction of oxidative stress and the effect of Al on phenolic metabolism, the maintenance of membrane stability and retardation of aging were guessed as the factors for growth stimulation or growth differences between Al treated and non-Al treated tea plants.