| 1. 14-year-old off-year bayberry (Myrica rubra Bieb.et Zucc) trees of 'Biji' cultivar from Yuyao were used to determine the changes of nucleic acid, IAA, proteins, lignin, carbohydrate, calcium and tryptophane, and the activities of nucleic acid hydrolases, IAA oxidase, lignin synthase, amylase and acid invertase in leaves of new shoots after GA3 spray during flower bud physiological differentiation and initiation in 1999. The results showed that flower bud physiological differentiation is in July, the peak period of which is in the second ten-day period of July, but flower bud initiation is at the end of July or at the beginning of AugustThe pattern of RNA level was a two-peak curve, but that of DNA level was an one-peak curve, which might symbol the vigorous gene transcription. The pattern of DNase activity was an one-bottom curve against the one-peak of DNA level, while the pattern of RNase activity was a two-bottom curve against the two-peak curve of RNA level. It was found that the level of RNA in leaves decreased with the cessation of vegetative growth before flower bud physiological differentiation. However, RNA accumulated sharply to the second peak, indicating an accelerated gene transcription and translation during flower bud physiological differentiation. GA3 increased RNase activity and depressed RNA level, although it had little effect on DNase activity and DNA level, so the total nucleic acid and the RNA/DNA ratio were lower than those of the control during flower bud physiological differentiation.The variations of protein levels were two-peak curves. The ratio of protein/RNA increased sharply, and proteins accumulated during flower bud physiological differentiation, whereas the levels of proteins declined during flower bud initiation. The accumulation of soluble protein was more lhan that of insoluble protein. GA3 decreased the content of soluble protein and 1he ratio of soluble protein/RNA.The variation of IAA content was also a two-peak curve, and the second peak occurred just before flower initiation. The variation of tryptophane content was almost reverse to that of IAA content The variation of IAA oxidase activity increased with the decline of IAA, and decreased with the accumulation of IAA during flower bud physiological differentiation. The peroxidase activity increased with the accumulation of IAA just before flower initiation, and decreasd with the decline of IAA during flower initiation. We thought that IAA was mainly controlled by IAA oxidase activity, and necessary for flower bud differentiation. GA3 inhibited the activities of IAA oxidase and peroxidase, and gave rise to a higher content of IAA, which subsequently led to the vigorous growth of new shoots and an unsufScient differentiation of flower buds.The activity of PAL increased to its highest level, Ihen did the activity of PPO before the peak of flower bud physiological differentiation. Both the activity of POD and the level of lignin increased to their highest levels during the peak of flower bud physiological differentiation, and decreased during flower initiation. GA3 inhibited the activities of PAL, PPO and POD, and slowed the biosynthsis of lignin.Starch, total soluble sugar and reduced sugar accumulated sharply before flower bud initiation, and were depleted during flower bud initiation. The variation of a - amylase activity was similar to that of starch content However, the variation of P -amylase activity was contrary to that of starch content It was thought that starch was degraded by both a - amylase and P -amylase independently. The variation of acid invertase activity was contrary to that of sucrose content, which increased significantly when acid invertase activity decreased sharply before flower bud initiation. GA3 increased the activities of a -amylase and acid invertase, but decreased 3 -amylase activity, and suppressed the56accumulation of starch, total soluble sugar and reduced sugar before flower bud initiationThe contents of total calcium and soluble calcium accumulated before flowe...
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