Study on Root Exudates of Sassafras tzumu Seedling Using Carbon 14

Sassafras tzumu seedlings were fed with carbon 14 and cultured in distilled water and nutritive solution respectively. During the period of culturing, distribution of photosynthates and root exudates in amount and in composition were detected everyday. The results are following: When 15 days after feeding, the photosynthesis production in seedling leaves reduced from 67.42% to 35.08% (in nutritive solution) and to 34.50% (in water), however, in new shoots and roots the photosynthesis production respectively increased by 10.87% and 14.5% (in nutritive solution),by 17.60% and 12.68% (in water).The summit of exudating occurred 3~5 days after labeling, afterwards, reducing gradually with time. During 10 days culturing, root exduades in accumulative amount is always more in water with sum 50 513 dpm per seedling than in solution with sum 45 586 dpm per seedling. Sugar is the main root exudate(60.03% in solution,59.70% in water), the organic acids the second, and amino acids is the least.