The Effects Of Leaf/fruit Ration On Growth, Development And Leaf Senescence Of Muskmelon(Cucumis Melo L.)

Pruning is primary measure of control growth and hasten fruiting in horticultural plant.Right pruning can improve structure of leaf system, and reduce the nutrient consumption of useless leaves. Right prunning can increase photosynthesis rate of leaf, and delay the senescence of plant. In open field, three cultivars of Cucumis melo L. var. inodorus, were used to study the growth and leaf senescence at different source /sink ratios.The results were summarized as following:1. The node longth, single leaf area evpanding and LAI increase at whole stage; Increasing the leaf-fruit ratio, the node longth and single leaf area decrease at each stage, leaf decrease can be compensated a little. LAI increase at same row spacing.2. As leaf numbers increased, fruit size, total soluble solids and flesh thickness increased, and then stabilized, pericarp thickness and fruit firmness showed no significant difference. But the index of fruit shape gradually decreased with the increase of leaf numbers. Fruit size and quality contributors will be affected signficantly when strength of source is small, and there have a threshold in fruit size, total soluble solids and thick of flesh.3. Although leaf decrease can be compensated a little by the increasing photosynthesis rate of single leaf, chlorophyll decomposes quickly and its content decreases, which accelerate the senescence of leaf.Although increasing the source /sink ratio makes photosynthesis rate of single leaf descend, chlorophyll decomposes slowly and its content keeps high, which delay the senescence of plant.4. Both protein and soluble sugar content of Huanghemi and Yinfeng decrease at whole stage , the content of MDA shows an opposite trend.; both protein and soluble sugar content of Yinxiang raised at first and then declined. Increasing the source /sink ratio significantly slows the leaf senescence. It indicates that the senescence of leaves is attributed to source /sink ratio.5. With further senescence, content of MDA increased; both content of soluble protein and chlorophyll decrease, the activity of SOD ,CAT,APX also decrease .The content of soluble protein and MDA of Yujinxiang were less than Huanghemi and Yinfeng's, the protected enzyme activities of Yujinxiang were more steadier than Huanghemi and Yinfeng's, and could alleviate the lipid peroxidation and delay the leaf senescence.