© 2000 Heron Publishing—Victoria, Canada
Allometric differences between current-year shoots and large branches of deciduous broad-leaved tree species
Maki Suzuki (1) and Tsutom Hiura (2, 3)
1. Tomakomai Research Station, Hokkaido University Forests, Tomakomai 053-0035, Japan / 2. Graduate School of Environmental Earth Science, Hokkaido University, Sapporo 060-0810, Japan / 3. Author to whom correspondence should be addressed (hiura@exfor.agr.hokudai.ac.jp) / Received January 28, 1999
Summary
Current-year shoots are mostly made of primary tissues, whereas first-order branches comprise mainly secondary tissues. Differences
in tissue composition of these units reflect differences in functional design. We compared the allometry of current-year shoots
and first-order branches in eight deciduous broad-leaved tree species and examined the functional differences underlying the
design of current-year shoots and first-order branches. Allometric relationships of first-order branches tended to be compatible
with predictions of the pipe model and elastic similarity model. That is, allometric constants of the relationships between
leaf mass and stem diameter at the branch base and between stem diameter and stem mass were 2.0 and 0.33–0.38, respectively,
indicating that the functional regulation of stem form of first-order branches can be predicted by the two models. However,
allometric relationships of current-year shoots were not compatible with the predictions of the pipe and elastic similarity
models. Thus, the allometric constant of the relationship between leaf mass and stem diameter at the base of current-year
shoots was larger than 2.0, and the allometric constant of the relationship between stem length and stem diameter of shoots
was larger than 1.0 in all species examined. However, current-year shoots had an allometric constant of leaf mass against
stem length that was less than 1.0, suggesting a functional demand on shoot design to reduce self-shading. Also, allometric
constants of stem length against stem diameter at the shoot base were larger in monopodial species than in sympodial species,
whereas allometric constants of leaf mass per shoot against stem length were smaller in monopodial species than in sympodial
species. We propose that the allometries of current-year shoots reflect their function as disposable units for temporary leaf
arrangement.
Keywords:
current-year shoot, first-order branch, functional demands on branch design, elastic similarity model, pipe model.
