| There were three experiments i.e. greenhouse, outdoor and field experiments. Three sugarcane varieties i.e. ROC22, ROC 16 and ROC 10, were employed as the plant materials for the experiments. Four concentrations of ethephon, i.e. 0mg/L, l00mg/L, 200mg/L and 400mg/L, were sprayed on the plant leaves at the young shoot stage (four to five leaves). The purpose of the study is to investigate the mechanism of ethphon on the tillering stimulation in sugarcane based on the physiological, biochemical and morphological charactes during the tillering stage. The main results were showed as follows:For the physiological and biochemical characters: 1. The ethephon treatments decreased the contents of Chl.a and Chl.b in short time after the treatment, but then turned to increase them and made them higher than those of the control. That is to say, the ethephon treatments showed promoting effects on the ratio of Chl.a to Chl.b. 2. The ethephon treatments increased the soluble sugar content in the radical stems, but it showed the opposite effect in the leaves. 3. The ethephon treatments showed an inhibiting effect on the water-solubility protein content of leaves in some time after the treatment, but then turned to show a promoting effect. But they showed a more strongly inhibiting effect in the radical-stems all the time. 4. Although the ethephon treatments decreased the protein content in the radical-stem cell wall, they showed stronger effect in certain time after the treatment. 5. The ethephon treatments increased the activity of H~+-ATPase and bound-ATPase in the leaves and in the radical-stems. 6. The ethephon treatments showed strongerpromoting effects on increasing the activity of CAT, POD", POD+ and IAA-oxidase in the radical-stems. 7. The 400mg/L ethephon treatment had more stable effect on promoting all the above activity of enzyme in the three sugarcane varieties. 8. The ethephon treatments showed effects of enhancing and inducing the expression on the isozymes of POD", POD+ and IAA-oxidase, and more marked effect was observed during the germination of the tillering-buds.For the morphological characters: 1. The ethephon treatments stimulated growing of the new roots at prophase in ROC22 and ROC 10, but then turned to inhibit them, and the 400mg/L ethephon treatment showed the strongest stimulating effect. Both the 200mg/L and the 400mg/L ethephon treatments stimulated the root ramifying. 2. The ethephon treatments promoted the expanding growth of the assumed stem at the early time, but inhibited it later. 3. The ethephon treatments decreased the plant height at first, and then turned to promote it and made it higher than those of the control finally. 4. The ethephon treatments accelerated the velocity of leaf growth, decreased the length, width and area of the leaves, increased the angle between the leaf and the stem, and stimulated the tillering-bud germinating and growing at prophase. The effect showed stronger with the ethephon concentration increasing. 5. The ethephon treatments increased the ratio of root to crown at the early tillering stage, and better effect was observed in the lOOmg/L ethephon treatment.For the agronomic characters and the cane yield in the field: 1. The ethephon treatments increased the tillering-stage rate and the tillering rate. As the ethephone concentration added, the effect showed stronger. 2. The ethephon treatments increased the effective tillering rate by 7.3-12.8% higher than that of the control, which contributed 22.8-30.2% and 38.4-39.5% to the cane yield in ROC22 and in ROC 16, respectively. 3. Both the lOOmg/L ethephon treatment in ROC22 and the 200mg/L ethephon treatment in ROC 16 showed the highest cane yield as compared with the others.According to the above results, we can make the following two conclusions:1. The ethephon treatments from 1 OOmg/L to 400mg/L had positive effecton stimulating the tillering-bud germination and promoting the plant growth, increasing the effective stalks from tillering and increasing the cane yield. 2. Under the condition of our pres...
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