© 2005 Heron Publishing—Victoria, Canada
Hydraulic conductivity, photosynthesis and leaf water balance in six evergreen woody species from fall to winter
Haruhiko Taneda (1, 2) and Masaki Tateno (3)
1. Department of Biology, Graduate School of Science, Osaka University, 1-1 Matikaneyama, Toyonaka, Osaka 560-0043, Japan / 2. Corresponding author (taneda@bio.sci.osaka-u.ac.jp) / 3. Nikko Botanical Gardens, Graduate School of Science, University of Tokyo, Nikko, Tochigi 321-1435, Japan / Received March 17, 2004; accepted August 14, 2004; published online January 4, 2005
Summary
To confirm that freeze–thaw embolism is a primary stress for evergreen woody species in winter, hydraulic conductivity, photosynthesis
and leaf water potential were measured during fall and winter in trees growing in a cool temperate zone (Nikko) and in a warm
temperate zone (Tokyo). We examined two evergreen conifers that naturally occur in the cool temperate zone (Abies firma Siebold & Zucc. and Abies homolepis Siebold & Zucc.), and four evergreen broad-leaved woody species that are restricted to the warm temperate zone (Camellia japonica L., Cinnamomum camphora (L.) J. Presl, Ilex crenata Thunb. and Quercus myrsinaefolia Blume). In Tokyo, where no freeze–thaw cycles of xylem sap occurred, hydraulic conductivity, photosynthesis and water balance
remained constant during the experimental period. In Nikko, where there were 38 daily freeze–thaw cycles by February, neither
of the tracheid-bearing evergreen conifers showed xylem embolism or leaf water deficits. Similarly, the broad-leaved evergreen
trees with small-diameter vessels did not exhibit severe embolism or water deficits and maintained CO2 assimilation even in January. In contrast, the two broad-leaved evergreen trees with large-diameter vessels showed significantly
reduced hydraulic conductivity and shoot die-back in winter. We conclude that freeze–thaw embolism restricts evergreen woody
species with large-diameter vessels to the warm temperate zone, whereas other stresses limit the distribution of broad-leaved
trees, that have small-diameter vessels, but which are restricted to the warm temperate zone.
Keywords:
freeze–thaw embolism, temperate forest, water stress, water transport, xylem anatomy.
