| Flower differentiation is one of the most important physiological processes in the growth and development of fruit trees. Studies on Calcium and Calmodulin are the most active field. In this research, Huanghua pear (Pyrus pyrifolia Nakai cv. Huanghua) was used for the experimental material in order to ascertain the changes and mechanism of Calcium and Calmodulin during flower differentiation. Natural growth of the trees was the control.. The growth regulator and the stimulant and inhibitor of Ca-CaM were used pressure trunk injection. The changes of Calcium and Calmodulin and corresponding nucleic acid, endogenous hormone, protein and carbohydrate were analyzed and compared.1. Sepal differentiation was observed between June10 and 28 in 1996.Induction of flower bud was between July 6 and 13, and primordial differentiation happened after July 22. On July 6, when the meristem changed quickly, cell layer of its corpus increased quickly. The scope and volume of cell layer of the quiescent zone rose and the volume of cell nucleus, especially the nucleolus, and chromatin in the karyolymph increased; The density of membrane structure became large. The number of mitochondrion increased while the volume of plastid reduced.2. Significant changes took place in the distribution of black particle of localization of Calcium ion, density and size with the procession of flower differentiation. The density of Calcium black particle was the smallest on June 28, when the sepal differentiation has finished, while it increased on July 6, the time for meristem growth, and then it decreased quickly, which could not be detected on July 22, the time for primordia differentiation. Before the meristem growth Calcium ions were partly distributed in the plastids while they were released to the cells, particuly to the nucleous after the meristem enlargement. The size of Calcium ions black particles decreased during the flower differentiation, which decreased quickly after July 6 and could not be detected on July 22.3. Changes of Calcium and calmodulin before and after flower differentiation showed that: There was an accumulation peak of Calcium content, which reducedduring flower differentiation, when it approached the meristem enlargement. Nevertheless, the peak of Calmodulin appeared after that of the Calcium content when the meristem enlarged and Calmodulin decreased after the induction stage. No significant changes took place in Calmodulin content, which was at a low level, before and after flower differentiation. With ripening and aging of the leaves the Calcium content rose in them, while the increase was slow during the induction of flower differentiation. The same changes of Calmodulin existed in the leaves on spurs and on new shoots whereas the former had a higher content of Calmodulin than the latter before and after the flower differentiation and formed a peak when the meristem enlarged.4. Changes of other physiological metabolite corresponding Calcium and Calmodulin changes in the buds were compared. The result suggested that the content of nucleic acid rose at the beginning of flower differentiation and had the upward tendency during the whole phase , which was especially obvious for RNA, and then decreased after August 4. As for ABA and GA, which reduced gradually after flower differentiation, certain accumulation was observed before flower differentiation .But before flower differentiation, ZR came to a tip and then had a sharp rise during the flower differentiation and then fell suddenly. Low protein and high carbohydrate accumulation were acquired before flower differentiatioa After flower differentiation, the protein experienced an abrupt increase and was at a high level during the whole period of flower differentiation despite that the carbohydrate was consumed steadily, and at a low level the same period.5. Changes of some other physiological metabolites corresponding the changes of Calcium and Calmodulin in the leaves were also compared and the results were as follows: the n...
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