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[E-2.2 Adaptation to Environmental Stresses in Tropical Rainforest Trees]

[Contact Person]

Yasushi MORIKAWA
Section Director of Plant Ecology,
Forest Environment Division, Forestry and Forest Products Research Institute
Ministry of Agriculture, Forestry and Fisheries
1 Matunosato, Kukizaki-machi Inashikl-gun Ibaraki 305 Japan
Phone +81-298-73-3211(Ext.353), Fax +81-298-74-3720

[Total Budget for FY1990-1992]

29,827,000 Yen

[Abstract]

　To estimate the effects of environmental factors on tree growth, water relation characteristics and ecophysiological processcs were studied for several dipterocarp tree species. The ability for maintaining positive turgor was relatively low in nursery seedlings. Open-grown tall trees had adapted morphologically to water stress as well as by maintaining positive turgor through osmotic adjustment. The adaptability to the water stress was lower in S. assamica compared with the other species. Oscilations of stomatal movement were observed in stomatal resistance after light exposure. Stomatal resistance become higher in the seedlings grown under low light illuminance. Such shaded condition may cause insensitive stomatal movement to abrupt environment changes. Stomatal conductance(Gw) in the morning was higher than in midday under natural condition. Maximum value of Gw of dipterocarps are relatively low(0.14 to 0.28cm・sec^-1) compared with Japanese broad-leaved tree species. Net photosynthesis rate at light and water optimum condition was lower in N. heimii than in H. odorata. Also, these values are relatively low compared with Japanese broad-leaved tree species. These results suggest that adaptation processes in gaseous exchange characteristics to water and light environments were different between dipterocarp species and Japanese broad-leaved tree species.

[Key Words]

Tropical forest, Dipterocarp Trees, Stomata Conductance, Water relations, Temperature-Photosynthcsis Curves