日本産ギボウシ属植物の生育場所と水分経済特性

抄録

To study the ecological adsptation of the Japanese Hosta, the habitat preference and water economic characteristics of a number of species are determined and compared. Stomatal density and size, transpiration rate, drought resistance and relative growth rate in seedlings are investigated as indicators of adaptation to the soil moisture conditions of the habitat. The species which commonly occur under a diversity of soil moisture conditions, for example, H. sieboldiana, can readily adapt their water economies to a wide variety of environments, showing fairly high transpiration rates, rather high drought resistance and high relative growth rates. They can be regarded as unspecialized in life. On the other hand, with the exception of H. capitata, the species restricted to relatively dry habitats such as outcrops and rocky soils, for example, H. kikutii and H. longipes. have low transpiration rates and low relative growth rates in spite of high drought resistance. Finally, H. longissima, which is confined to wet places, exhibits low drought resistance, with a high transpiration rate and a somewhat high relative growth rate. The species which grow in limited habitats have rigid water economics, though each is well adapted to its particular environment. Thus, they may be considered ecologically specialized.