PARENT SESSION
Poster Session 1: Photosynthesis and Water Relations
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Responses to cyclic dehydration and rehydration in the potted saplings of invasive and native trees in subtropical islands.
Yazaki, Kenichi*,1, Sano, Yuzo2, Fujikawa, Seizo2, Ishida, Atsushi1, 1 Forestry and Forest Products Research Institute, Tsukuba, Ibaraki, Japan2 Graduate School of Agriculture, Sapporo, Hokkaido, Japan
ABSTRACT- The Bonin islands, in the western Pacific of Japan, has relatively lower precipitation than in other subtropical region in Japan. For tree saplings in the islands, the tolerance to prolonged drought and the immediate recovery from dehydration after temporal rainfall are important for their survival. Trema orientalis distributes in mesic area, but Psidium cattleianum is distributes even in relatively arid area and is an invasive success tree in the islands. We evaluated water use for the saplings of T. orientalis and P. cattleianum saplings under controlled cycles of drought and irrigation in a phytotron. The potted nine-month-old saplings were grown for fifteen days without irrigation, following which they were irrigated for two days. We furthermore repeated this water treatment two cycles. We determined the number of leaves, transpiration rate per unit leaf area (Tr), and leaf water potential at daytime (
d) every five day during the cyclic treatments. We also observed the time course of the distribution of water in xylem of the stems with a cryo-scanning electron microscope. For T. orientalis saplings defoliation and xylem cavitation were found from day 10 following the drought treatment. The xylem cavitation immediately recovered just after rehydration. In contrast, any defoliation and xylem cavitation were not found for P. cattleianum. The values of d at drought periods and Tr just after rehydration were tended to be lower for P. cattleianum than for T. orientalis We concluded that T. orientalis saplings can not survive under prolonged drought because of their defoliation and vulnerability to cavitation, whereas P. cattleianum can survive even under prolonged drought by their conservative water use.
Key words: pulse irrigation, water relations, leaf gas exchange, xylem anatomy