Effect of the Replacement of Potassium by Sodium on the Sugar Content and the Activity of Related Metabolic Enzymes in the Coconut Leaves

Key words: 
• coconut /
• Na_K replacement /
• sucrose /
• soluble sugar /
• sucrose synthase /
• sucrose phosphate synthase

Abstract: In order to study the change of sucrose content and related metabolic enzymes activity under the condition of the different proportional replacement of potassium by sodium in the coconut leaves,a test was attempted in which the replacement of potassium by sodium in the coconut leaves was carried out under the sand culture. The result showed that: in a condition of which the total concentration of potassium and sodium was 4 mmol·L^-1, the change of the content of sucrose and soluble saccharide,as well as the activity of sucrose synthase and sucrose phosphate synthase,was similar to the control in the treatments of 25% and 50% replacement of potassium by sodium ; not only the tendency was gradually steady and but also the difference between them was not significant in the later period（P ＞ 0. 05）. However,compared to the control, the contents of sucrose and soluble saccharide and the activity of sucrose synthase reduced gradually in the treatments of 75% and 100% replacement of potassium by sodium,except that the change of the activity of sucrose phosphate synthase was as similar as the control. The results of the study expound that the partial replacement of potassium by sodium had no effect on the contents of sucrose and soluble sugar and the activity of related enzymes in coconut seedlings,which provides stable carbon sources for carbon metabolism,so as to ensure the normal growth of plants.