Studies On Primary Thickening Growth Mechanism Of Phyllostachys Edulis Shoot Bud

The plant anatomical and statistical methods were applied to investigate the primary thickening development of Phyllostachys edulis shoot buds. The results were as follows:1. The developmental process of the shoot bud could be divided into four stages: the dormant stage, the germinating stage, the development stage and the mature stage. The development stage contained three sub-stages: the early development stage, the middle development stage and the late development stage. The shoot bud already became a mature shoot in the mature stage. The middle development stage and the late development stage were the most complicated of all in the tissue differentiation, within which the shoot bud formed all structures.2. The primary thickening growth of Phyllostachys edulis shoot bud was a successive course. It began before the elongating of the internode and ended before the completion of the elongation of the internode. In the primary thickening process of the Phyllostachys edulis shoot bud, the contributions of different tissues were arranged as follows: pith meristem> vascular tissue> ground tissue> cortex+ epidermis. The main factor of the primary thickening process is the proliferation and the increase of pith cells. The forming of the sclereified boundary tissue around the pith signaled the end of the development of the pith meristem. And that the number and volume of the cells of the ground tissue didn't change signaled the end of the primary thickening process of the shoot bud.3. The primary thickening process of the shoot bud wall was also successive, which was contained in the primary thickening process of the shoot bud. In the primary thickening process of the shoot bud wall, the contributions of each tissue were arranged from big to small as follows: vascular tissue> ground tissue> cortex+ epidermis. The main factor of the primary thickening process is the differentiation and development of the vascular tissue.4. There was no primary thickening meristem in the apex of the Phyllostachys edulis shoot buds which were differentiated by vegetative propagation. All various parts of the shoot bud structures were from the apical meristem. The apical statuses of different developmental stages of the shoot buds were different. The new tissues which were differentiated from the various apexes were also different. The apex mainly formed procambium and ground tissue before early development stage, pith meristem in the later development stages.5. The order of pith meristem and vascular tissue was endarch. The pith meristem was directly differentiated from the corpus. The longitudinal procambiums and ground tissue had the same origin, all indirectly from the corpus. The procambiums in diaphragm were from the left meristematic cells of the apical meristem and their differentiations were later than those in the shoot bud wall.