Poster: Ecophysiology

Abs # 10: Leaf senescence of Quercus crispula under different growth conditions

Presenter:	Ono, Kiyomi , kiyomion@pop.lowtem.hokudai.ac.jp
Authors	Ono, Kiyomi  (A)   Etoh, Noriko  (A)   Hara, Toshihiko  (A)
Affiliations:	(A): Insititute of Low Temperature Science, Hokkaido University

Leaf senescence is influenced by the availability of nitrogen and carbon, and their utilization within the plants. In leaves of plants grown under a stressful condition such as low temperature and high light intensity, the oxidative stress probably affects leaf senescence. To investigate how growth temperature affects leaf senescence, Quercus crispula plants were grown from seeds in growth chambers at two temperatures (25C, 15C) under the low light intensity (100 μmol m^-2 s^-1) without nutrient supply. Photosynthetic rates and chlorophyll contents gradually decreased after the full expansion of the leaves under the both growth temperatures. Increases in dry weights of roots and whole plants were higher in plants grown at 25C. Thylakoid membrane-bound ascorbate peroxidase activities based on chlorophyll increased gradually after the full expansion of the leaves of plants grown under the both temperatures. The xanthophyll cycle pool size tended to be larger in leaves of plants grown at 15C. How plant growth and oxidative stress affect leaf senescence will be discussed.