||The growth of new culms and the seasonal changes of photosynthetic ability were investigated. 1) The new culm of Suzutake begins to sprout when the daily mean soil temperature at the depth of 10 cm go... up to about 10℃ and finishes its elongation within two months. 2) After the completion of culm-elongation, the new leaf begins to unfold and finish it completely by ten days or more. The unfolding of all leaves have been completed within 30～50 days following the first-leaf appearance. 3) The phtosynthetic ability of new leaves is higher than in any old leaf. 4) As the optimum condition in photosynthesis, temperature should be about 20℃ and light intensity, 30 klux and more. 5) Although the photosynthetic ability of a new leaf continued to increase until late in the first growing season, it decreases rapidly at a temperature below O℃. The decreased photosynthetic ability hardly recovers. 6) It became evident that the photosynthetic ability of shade leaf is higher than that of a sun leaf in low light intensity and Suzutake was found to be a shade-enduring plant.