Some Physiological Changes during Growth of Over-summer Tomato

During growth of over-summer tomato, the content of chlorophyll in leaves and the root activity of tomato increased stage by stage. Root activity of tomato cultured in the open was lower at early growth stage, but the result was opposite at fruiting stage, and the chlorophyll content of tomato cultured in the open was kept higher level at the whole growth stage. The contents of malondialdehyde (MDA), a product of membrane-lipid peroxidation in tomato leaves in summer was higher at noon. But the level of membrane-lipid peroxidation of tomato cultured with maize and under shading was lower than in the open. SOD activity increased at morning gradually, and kept a high level at afternoon. At summer, the photosynthetic rate was different with the different cultural manner, that of tomato cultured in the open was higher than cultivation with maize and under shading at morning, but the noon depression was serious, and after noon the result was opposite. The Fv/Fm of tomato cultured under shading was decreased less than in the open at noon, this manifested photo-inhibition of photosynthesis of tomato cultured under shading was less.