Abstract: The ultrastructural localization of adenosine triphosphatase (ATPase) activities in stigmatic cells in various developmental stages of PopUlus lasiocarpa was investigated using the cytochemical method Of read phosphate precipitation. The results show as follows: 1. Lead deposits which marked the ATPase activities were observed on the pellicle of stigmas. The ATPase activities greatly increased in receptive stage, but they were few or even absent in young and old stages. The changes Of pellicle ATPase strongly exhibited that ATPase was correlated with the pollen-stigma interaction. 2. In the stigma ceils inreceptive stage, ATPase was mainly located at mitochondria cristae, chloroplast lamellae and endoplasmic reticulum. Lead deposits were also visible on the plasmalemma, plasmodesma, nuclear membrane and in nucleoli. No lead deposits were found on dictyosome and vacuole membrane. 3. During the degeneration of stigmatic ceils; the location of ATPase changed. The distribution of ATPase was in vacuole membrane, digestive vesicle, mitochondrium envelop, chloroplast envelop, and digested fragment. The mitochondrium cristae and chloroplast lamellae where ATPase was the most active in previous stage now lost their ATPase activities.

Key words: ATPase, Pellicle, Stigmatic cell, Populus lasiocarpa