J Integr Plant Biol. ›› 2000, Vol. 42 ›› Issue (5): 455-460.

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Ultracytochemical Localization of ATPase During the Secondary Xylem Differentiation and Dedifferentiation in Eucommia ulmoides Trunk

  

Abstract:

The ultracytochemical localization of ATPase in the secondary xylem cells during their differentiation and dedifferentiation in the girdled Eucommia ulmoides Oliv. was carried out using a lead phosphate precipitation technique. Throughout the differentiation, which is a typical programmed cell death (PCD) process, ATPase deposits increased in the nucleus but decreased and progressively disappeared in the cell organelles. At the same time, the distribution of ATPase increased in the inner face of the cell wall and pits with cytoplasmic degeneration. The results demonstrated that the PCD was an energy dependent active process and was controlled by nuclear genes. On the other hand, the distribution of ATPase in the intercellular spaces increased with the formation of the new cambium resulted from the dedifferentiation of the secondary xylem cells after girdling. However, ATPase was not found in the nucleus of the dividing cells, suggesting that nutrients were transported through protoplast during differentiation, and through both protoplast and apoplast during dedifferentiation. Thus, the energy required in cell division was provided mainly by intercellular spaces. These findings indicate that the dynamic distribution of ATPase reflected which cell component was actively taking part in the cell metabolism at various stages of the plant development, and its distribution was associated with the physiological state of the cell. Based on the characteristic distributions of ATPase, the critical stage of cell differentiation and the relationship between the critical stage and dedifferentiation were discussed.

杜仲次生木质部细胞分化和脱分化过程中ATPase的超微细胞化学定位
王雅清   Kalima-N,Koma MWANGE 崔克明*

(北京大学生命科学学院,北京100871)

摘要:采用磷酸铅沉淀技术,对杜仲(Eucommia ulmoides Oliv.)次生木质部细胞分和脱化过程进行了ATPase的超微细胞化学定位。随着分化过程中细胞程序性死亡(programmed cell death,PCD)程度的加深,ATPase在细胞核上的分布由少变多,而在各种细胞器上的分布由有到无,并且随着细胞质的解体,ATPase在细胞壁内侧和纹孔处的分布也由少到多,说明它们的变化是由核基因控制的主动需能过程;杜仲剥皮后的脱分化过程中,随着细胞开始分裂进而迅速分裂形成新的形成层,胞间隙和胞间层中ATPade的分布由少到多,但分裂细胞的核上无此酶分布,可
能细胞由分化向脱分化转变时,物质运输由单一的共质体运输转变为共质体运输和质外体运输两种途径,并且这些细胞代谢所需的能量可能主要来自胞间隙和胞间层。以上结果说明,ATPade的分布反映了某一时空内哪些细胞组分在活跃地参与细胞代谢及个体发育过程,其分布是与细胞的生理状态相对应的,即是受遗传程序控制的。此外,根据酶的分布特点,探讨了细胞分化临界期的指标及其与脱分化的关系。
关键词: 杜仲;次生木质部;分化;脱分化;细胞程序性死亡(PCD);ATPase

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