SEASONAL-CHANGES OF CARBOHYDRATE AND NITR OGEN STATUS IN MULBERRY TREE

The changes of carbohydrate and nitrogen contents were determined in t wo-year old Taisang 2 mulberry tress (Mours alba L. var. acidosa G.) a fter pruning in four seasons from July 1992 to June 1992. Trunks and r oots contained higher contents of total carbohydrates,starch and ethan ol-soluble sugars in the winter than in the other seasons. Total carbo hydrate and starch contents decreased immediately after each Seasonal pruning, followed by a steady increase up to the next pruning treatmen t. On the contrary, the post -pruning changes in contents of ethanol-s oluble sugars in the turnks and roots showed the tendency of an initia l increase with a subsequent decrease. The only exception was in autum n season where ethanol-soluble content increased continuously after pr uning treatment. The contents of total nitrogen, protein nitrogen,and water-soluble nitrogen in the trunks and roots were higher during the winter season from December to March. Pruning showed a significant inf luence on the changes in N-containing compounds in the roots. For the newly-developed shoots and leaves after pruning, the contents of total nitrogen, protein nitrogen, and water-soluble nitrogen increased mark edly for a short period of time, and then decreased drastically until the next pruning treatment. However, the contents remained at a steady state, or increased slightly, during the winter season.