Abstract: The seasonal and age-related changes in leaf water potential of Moso bamboo (Phyllostachys edulis) under drought stress were examined under long-term precipitation exclusion treatment using the “ceiling method”, aiming to provide a theoretical basis for the sustainable management of Moso bamboo under climate change. The results showed that under the drought treatment, except for the predawn leaf water potential of bamboos with age of degree I in autumn being greater than that of the control, the predawn and midday leaf water potential of bamboos with different ages were all lower than those of the control across all seasons. The predawn leaf water potential of all aged bamboos under control and drought treatments and the midday leaf water potential of all aged bamboos under control were gradually decreased over season. The midday leaf water potential under drought was decreased first, then increased, and then decreased. The annual average of predawn leaf water potential under control increased first and then decreased with increasing bamboo age, whereas that under drought and the midday leaf water potential under drought and control treatments gradually decreased. Across all the treatments, the predawn leaf water potential in summer and winter consistently decreased with increasing bamboo age. With increasing bamboo age, the predawn leaf water potential showed an ‘N’-shaped variation in spring, an ‘M’-shaped variation in autumn under the control, and a pattern of first decrease, then increase, and then decrease in autumn under drought. There was a significant difference in the predawn leaf water potential of bamboo between age of degree V and ages of degree Ⅰ to Ⅲ separately in winter under drought and control treatments (P<0.05). The midday leaf water potential of bamboos under drought stress and control treatments in different seasons was generally the lowest for bamboo with age of degree IV or V, and the highest for bamboo with age of degree Ⅰ or Ⅱ. There was a significant difference in the midday leaf water potential of bamboo between degree Ⅰ and Ⅴ in autumn and winter (P<0.05). The seasonal changes in predawn leaf water potential were consistent across all treatments for different aged bamboos. Under drought, the midday leaf water potential of bamboos with ages of degree Ⅱ and III first increased and then decreased over seasons, while that of the control with age of degree Ⅱ and III gradually decreased. The highest water recovery capacity of bamboos with age of degree I in all treatments occurred in summer. For bamboos with ages of degree Ⅱ, Ⅲ, and Ⅴ, it occurred in spring. For bamboos with age of degree Ⅳ, it occurred in summer (under drought) and autumn (control). Bamboos of various degrees had a high ability to withstand drought stress in winter under all treatments.

Key words: Phyllostachys edulis, long-term drought, predawn leaf water potential, midday leaf water potential, season, age