Abstract: With several microscopic and cytochemical methods, the ultrastructure modification and ultracytochemical localization about some enzymes like H+ -ATPase , Ca²⁺ -ATP_ase and acid phosphatase (AP_ase ) of fiber in Phyllostachys edulis culms during secondary wall formation were studied. Early, intact double karyotheca remained in fiber nucleus, while nuclear chromatin agglutinated. A lot of organelles such as mitochondria, rough endoplasmic reticula and Golgi bodies were observed in fiber cell. Then, double karyotheca disappeared , and the organelles disintegrated. Multivesicular bodies appeared in fiber cytoplasm. With the further development of fiber, fiber wall underwent continual thickening with aging, and polylaminate structure gradually appeared. While the agglutinated nucleus, transfer vesicles, plasma membrane and plasmodesmata still presented. During the secondary wall formation of fiber, H⁺ -ATP_ase , Ca²⁺ -ATP_ase and AP_ase also sustainablely remained in plasma membrane, plasma membrane invagination, plasmodesmata, transfer vesicles and agglutinated nucleus. The results demonstrated that (1) the fiber cell of P. edulis culm is a special long-lived cell, which differs from that of woody dicotyledons, and (2) the sustainable persistence of ATPase and APase in fiber protoplast is closely correlated
to the continual thickening of secondary wall with ageing .

Key words: Long- lived cell