Effects Of Ethephon Sprayed At Early Growth Stage On Root Physiologica Characters And Shoot Metabolism Of Carbohydrate And Nitrogen In Sugarcane

Two sugarcane varieties, i.e. GT17 and ROC22, were employed as the plant materials. Ethephon of three concentrations, 0 mg/L, 100mg/L and 200mg/L, were sprayed on the plant leaves at early growth stage in the field experiment. In the same time, two concentrations of ethephon were used in a pot trial. The root growth and some physiological characters were measured, and their relationships with shoot metabolism of carbohydrate and nitrogen were determined. The major agronomic characters were investigated.For the lOOmg/L ethephon treatment, the length and dry weight of roots were apparently increased at first, but this effect diminished gradually as compared with the control. This treatment also promoted the activities of roots, decreased the activity of peroxidase in root tips.The 100 mg/L and 200 mg/L ethephon treatments increased the quantity of the bleeding sap, and more stable effect was observed in the lOOmg/L ethephon treatment. The ethephon treatment increased cytokinin (zeatin) concentration in the bleeding sap, and the 200mg/L ethephon treatment showed the highest. This might indicate that the plants treated with ethephon had stronger ability to produce cytokinin (zeatin) in their root systems. The ethephon treatment also had higher potassium content in the bleeding sap of each plant, and the lOOmg/L ethephon treatment showed the highest. The results of electroconductivity showed the same trend as those of potassium in the bleeding sap of each plant. These results suggested that the ethephon treatment increased the absorption ability to water and mineral elements as compared the control.For GT17, the treatment of 100 mg/L ethephon decreased some physiological characters that were related with nitrogen metabolism, that is, NRA activity, soluble protein and nitrogen contents in the leaves, at first, and then turned to promote them and made them higher than those of the control.The contents of phosphorous, potassium and soluble sugar, and the plant height showed the similar effects to the nitrogen. For ROC22, the 100 mg/L ethephon treatment promoted nitrogen metabolism all the time, but no promotion was observed for soluble sugar content in the leaves. The physiological characters related to metabolism of nitrogen and carbohydrate were fluctuated in the 200 mg/L ethephon treatment for both varieties.