The Cytobiological Study On The Initiation And Development Of Vascular Cambium In Populus Deltoides

The initiation and development of Populus deltoides was studied first by using optical microscope and electron microscope in detail. The results were:1. The transition from procambium to cambium was a gradual process in the stem tip, and the ultrastructural feature changed by degrees. When internode elongation nearly was stoped, and the development of leaf was matured, the transition has almost completed.2.The vascular cambium was non-stratified. It has only one initial cell layer. The fine structure and sequence of events of mitosis in the dividing cambial cells apparently were similar to those of dividing cells in root and stem tips. Of special interest was the observation that during cytokinesis, a broad cytoplasmic plate preceded along the bundle of cytoplasm.3. The secondany xylem mother cell of vascular cambium were differentiated into vessels,gelatinous fibre,libriform fibre, and parenchyma cell. The differetiation process of tracheary elements was divided into three phases: â‘ The radial expanding of cell; â‘¡The forming of pit bordered and secondary cell wall; â‘¢The lysising of protoplasm.4. The secondary phloem mother cell were divided and differentiated into sieve tube,companion cell,libriform fibre, parenchyma cell,and a few sclereid cells,The sieve tube and companion cell was originated from inequality mitosis of sieve mother cell. The process of development of sieve tube was divided into three stages according to the lysising of tonoplast and plasmic membrane:â‘ Immature stage; â‘¡Mature stage;â‘¢The stage of decline. It appears to companion cell that the cellular feature was typical programmed cell death in the stage of decline of sieve tube.