| Two sugarcane varieties, i.e. ROC 16 and ROC22, were employed as the plant materials in the field experiment. Three concentrations of ethephon, i.e.0mg/L, 100mg/L and 200mg/L, were sprayed on the plant leaves at early tillering stage. The dynamic changes of IAA, CTK in stems were determined with high-performance liquid chromatography (HPLC). The activities of peroxidase, IAA oxidase and acid invertase in stems were measured. The differentiation of vascular bundles was observed. The contents of soluble sugar, soluble protein, free amino acid, nitrate and calcium in bleeding sap from the stems were detected. The tillering rate and late tillering rate were investigated. The results indicated that foliar spray of ethephon stimulated the plant tillering for both tested sugarcane varieties especially for ROC 16, which was closely related to the changes of hormones, enzymes and nutritions in the plants. The main results were showed as follows.1. The highest tiller rate and late tiller rate were found in the treatment with 100mg/L ethephon. The treatment with 400mg/L ethephon did not increase tillering in the present study.2. Foliage application of 100mg/L ethephon at tillering stage resulted in decreasing of the IAA content in stem tips and increasing of the CTK content in roots. As a result, the ratio of CTK to IAA in bleeding sap became higher as compared with the control. The variety ROC22 showed a wider change than ROC 16. The results for the treatment with 400mg/L ethephon was oppsite to those of the treatment with 100mg/Lethphon.3. Foliage application of 100mg/L ethephon increased the activities of peroxidase and IAA oxidase and decreased that of acid invertase in roots. The treatments with 100mg/L ethephon recorded higher activities as compared with those with 0mg/L and 400mg/L ethephon.4. The treatment with 100mg/L ethephon accelerated the differentiation of vascular bundles and increased the density bundles in stems as compared with the treatments with 0mg/L and 400mg/L ehtephon. But smaller area of vascular bundles and diameter of epigenetic vessel were observed in the treatment with 100mg/L ethephon. The treatment with 400/L ethephon showed an obvious inhibition effect.5. The free amino acid content in bleeding sap from stem was lower in the treatment with 100mg/L ethephon than those in the treatments with 0mg/L and 400mg/L ethephon. For the nitrate content, however, it was higher in the treatment with 100mg/L ethephon than in the treatments with 0mg/L and 400mg/L ethephon, and it was more effective for ROC22 than for ROC 16. The highest nitrate content was observed in the variety ROC22 treated with 100mg/L ethephon. The contents of soluble sugar and soluble protein in bleeding sap from stem showed fluctuating. They were lower at first, but higher then, and again lower later in the treatment with 100mg/L ethephon than in the treatments with 0mg/L and 400mg/L ethephon, respectively, although the fluctuating time was different for both varieties. The ethephon treatment had very little effect on the calcium content for the variety ROC 16. For the variety ROC22, however, the treatment with 100mg/L ethephon recorded obviously higher calcium content than both the treatments with 0mg/L and 400mg/L ethephon while the the treatment with 400mg/L ethephon lower than the control. |
