| Using the method of nutrition culture, the characteristics of aluminum absorption of Longan, the effects of aluminum stress on the growth, cell ultra-structure, some physiological and biochemical response in related to carbon, nitrogen, AOS, and endogenous hormone , content of PAs, and secretion of root was studied in the thesis. The main results were submitted as follows:1 The study on the characteristics of aluminum absorption.1.1 Studies on the curves of aluminum absorption and the effect of 2,4--DNP on the aluminum absorption showed that the characteristics of aluminum absorption depended on the concentration of aluminum in the medium. At the low concentration (<0.370mmol.L-1), aluminum uptake were dominated by metabolism. When aluminum concentration is higher than 0.370mmol.L-1, aluminum uptake was mainly controlled by non-metabolic factors.1.2 Under aluminum stress, the aluminum taken by Longan mainly accumulated in root. The content of aluminum in root is as 3.54-5.66 times as that in stem, and as 3.60-5.80 times as that in leaves. As the concentration of aluminum in the medium increasing, the content and accumulation of aluminum in root increased greatly, however, the part taken by root and transferred to up-ground decreased.1.3 The aluminum mainly distributed in cell wall of Longan leaves. Under the aluminum stress, the content of aluminum in different parts of cell was in the order as: cell wall>cytoplasm>chloroplast>mitochondrion>nuclear protein. The content in cell wall is highest, which reached to 86.20%-88.58% of total accumulation. This kind of distribution model of aluminum in Longan leaves was helpful for preventing them from damage. It can also restrain redundant aluminum getting into the cell which might cause the fateful damage on cell parts, such as chloroplast and mitochondrion.1.4 Aluminum ion mainly existed in cord form, and it existed in freedom form only accounted for 6.68%-7.13% of total aluminum in leaves of Longan . However, amount of aluminum in cord form was nearly equal to that in freedom form in root whatever the concentration is high or low in the medium. Therefore, the degree of damage was decided by the total amount of aluminum.2 The effects of aluminum stress on growth and cell ultra-structure of leaves and roots.2.1 Under aluminum stress, the seedling growth was restrained. Aluminum toxicity had been caused only as the concentration of aluminum reached to 0.185mmol.L-1, and the more theconcentration increased, the more the toxicity was. Because of aluminum stress, the biomass of root, stem, and leaves decreased 13.8%-31.7%, 5.4%-36.2%, and 14.5%-58.2%, the area of leaves decreased 13.5%-46.5%, the activity of root decreased 22.0%-66.0%, and the ratio of water in root, stem, and leaves decreased 2.3%-4.8%, 7.3%-17.8%, and 1.5%-6.0% respectively.2.2 Aluminum stress caused damage on the cell ultra-structure of Longan leaves. The damage on chloroplast suffering from aluminum stress was most distinguished. Under aluminum stress, membrane system of chloroplast damaged greatly, grana lamellae twisted and disordered. It was also found that the cytoplasm segregated from cell wall and the cell wall began to decompose, the clearance between cells became smaller, the vacuole lamellae broke, and the vacuole disappeared under aluminum stress. At the same time, the membrane system of mitochondrion destroyed, and the number of cristae reduced and even disappeared.2.3 Under aluminum stress, the apices of root enlarged, the tip of root became shorter and thicker. The damage suffering from aluminum caused different degree crack on surface of root, and this kind of damage became more serious as the concentration of aluminum increased. Meanwhile, the cell wall of root enlongation part decomposed, the clearance between cells shorted, and the cell wall lost elasticity and became harder. The membrane system were destroyed, the cytoplasm segregated from the cell wall, and the lamellae of nucleolus and mitochondrion suffered disruption. The numb...
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