Response Of Three Aluminum-Tolerant Plants To Aluminum Toxicity

1. Lower concentrations of aluminum (10～100mg·L^-1) soaking could enhance germination index and vigor index and promote germination of buckwheat (Fagopyrum esculentum Moench) seeds by decreasing the membrane permeability and the leakage of nutritive substance in seeds. Aluminum could inhibite the root growth, but had less effect on both above-ground and under-ground biomass.2. Buckwheat had a high ability for aluminum absorption and accumulation. Based on a ²⁷Al-NMR analysis, [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂] was widely distributed in buckwheat. Except [AlO₄Al₁₂(OH)₂₄(H₂O)₁₂], Al-citrate, Al-oxalate(1:1), Al-oxlate(1:2) and Al-H₃PO₄ could be detected in the roots and Al-citrate in leaves and stem. Free Al in the symplasm was potentially phytotoxic, but the chelator could bind aluminum very tightly in cytosol and protect the cytosol against aluminum injury. Nonphytotoxic form of aluminum was responsible for high Aluminum tolerance in plants.3. Although buckwheat could absorb and accumulate aluminum in environment, aluminum stress could inhibite the absorption of other nutrient elements, especially N, P, K, Ca and Mg. Accordingly, less nutrition elements were transportated to leaves from roots. As the concentrations of aluminium were increased, the inhibition was enhanced.4. The composition and quantity of buckwheat root exudates were changed in aluminum stress. The exudation of soluble sugar increased with the increasing of aluminum concentration. The change of exudation of amino acid was similar with the exudation of soluble sugar when the aluminum concentration was lower than 0.1g·kg^-1 sand, but the variation of different kinds...