Studies On The Differention And Function Of Ground Tissue In Bamboo Culms

The development of ground tissue in bamboo(Phyllostachys edulis) culms were systematically investigated with methods and technologies of cell biology. The marked differences between the long cell and the short cell were elucidated. And the mechanisms of ground tissue differentiation and development and the physiological functions of the long cell and the short cell were discussed.The results indicated that the development of ground tissue was classified into four stages based on the light microscopy observations: initiating stage, dividing stage, elongation stage and maturation stage. Some cells of the ground tissue began elongation at early dividing stage,but short cells had no elongation and remained active metabolism. And the longer cell was farther from the short cell. The above observations indicated that the short cell was meristematic as the gound meristem cell, and ground tissue might come of the short cell.The observations by polarized light microscope showed that secondary walls formed at the late stage of elongation, indicating that the secondary walls began to be laid down while the long cells were still undergoing elongation, suggesting that it might act to cause the slow down and eventual cessation of cell elongation.There were significant differences between the secondary walls of long cells and those of the short cells. The long cell walls underwent thickening with aging. In the former four years, long cell walls had a marked thickening, subsequently, the degree of thickening decreased gradually. The long cell walls formed gradually the polylamellate structure in alternate arrangement of broadly light lamellae with deposition of cellulose in growing period and narrowly dark lamellae, which mainly deposited lignin in relative dormancy period. And lignin in the long cell walls increased with age. It is significant to increase the mechanical strength of the bamboo culms.But the secondary wall and lignificated regions of the short cells were only confined to the portion in contact with the long cell walls, while the walls at the corner region remained the state of primary wall in mature culms. And there was no thickening, the polylamellate structure and lignin increase with age in the secondary walls of the short cells. The short cell remained in the young state during the development except for the partial secondary wall.During the development of the gound tissue, mature long cells lost some of the organelles, while the short cell remained plentiful mitochondria, endoplasmic reticulums and transfer vesicles indicating the active metabolism.The long cell was a reservior where the energy is stored in the form of starch granules. Whereas the short cells remained no starch granule accumulated and had active physiological metabolism.ATPase activity in mature long cells declined. On the other hand, the short cell remained high ATPase activity, especially in the plasma membrane, transfer vesicles, pits and intercellular spaces, indicating the short cells had active exchange and transport with other cells chiefly by symplastic transport and apolastic transport suggesting that the short cell functioned in transport.Peroxidase activity concentrated in the narrow lamellae of the long cell walls,where lignin mainly deposited, especially in the first relative dormancy period. The peroxidase activity in the narrow lamellae of the long cell walls declined gradually with aging. So the peroxidase in the long cell walls took part in the synthesis and deposition of lignin. But the short cells differed from the long cells and always had peroxidase activity. Also, Peroxidase in the short cells perhaps took part in the synthesis of lignin in the long cell walls and the elimination of reactive oxygen.