Abstract: Ultrastructural changes in secondary wall formation of Phyllostachys pubescens Mazel fiber were investigated with transmission electron microscopy. Fiber developed initially with the elongation of cells containing ribosomes, mitochondria and Golgi bodies in the dense cytoplasm. During the wall thickening, the number of rough endoplasmic reticulum and Golgi bodies increased apparently. There were two kinds of Golgi vesicles, together with the ones from endoplasmic reticulum formed transport vesicles. Many microtubules were arranged parallel to the long axis of the cell adjacent to the plasmalemma. Along with the further development of fiber, polylamellate structure of the secondary wall appeared, with concurrent agglutination of chromatin in the nucleus, swelling and disintegration of organelles, while cortical microtubules were still arranged neatly against the inner side of plasmalemma. Lomasomes could be observed between the wall and plasmalemma. The results indicated that the organelles, such as Golgi bodies together with small vesicles, rough endoplasmic reticulum and lomasomes, played the key role in the thickening and lignification of the secondary wall of bamboo fiber, though cortical microtubules were correlative with the process as well.

Key words: secondary wall formation, ultrastructure, organelle, fiber, Phyllostachys pubescens