© 2003 Heron Publishing—Victoria, Canada
Adaptive significance of C partitioning and regulation of specific leaf area in Betula pendula
Kai W. Wirtz (1)
1. Institute for Chemistry and Biology of the Marine Environment (ICBM), University of Oldenburg, P.O. Box 2503, 26111 Oldenburg,
Germany (wirtz@icbm.de) / Received January 28, 2002; accepted July 27, 2002; published online January 31, 2003
Summary
Carbon allocation and regulation of specific leaf area (σ) define key processes underlying the adaptation of plants to varying
habitats. In this study, the general principles governing adaptation and a dynamic optimality model of plant adaptation are
reviewed. The central new elements of this model are: (i) differential root carbon costs for maintaining a defined nutrient
status; (ii) a simple formula for optimal σ at steady-state as a function of nitrogen (N) status and irradiance; and (iii)
generic rules for the time propagation of adapting traits. The model was applied to a large data set compiled by Ingestad
et al. (1995) and McDonald et al. (1986a, 1986b) for birch seedlings (Betula pendula Roth) during stationary logarithmic growth and during transient changes in response to a range of irradiances and nutrient
supply rates. In the stationary case, large variations in the fraction of leaf dry mass to total dry mass (fL), σ and N concentration were simulated with high accuracy. The independently calibrated model described the temporal response
of seedlings following a sharp decrease in N supply, which includes phenomena such as the temporary C accumulation in leaves
and damped oscillations in N concentration. Dynamics in σ were more sensitive to variation in light than in N supply. Nevertheless,
adaptive adjustments in fL, σ and N concentration were strongly coupled, underlining the relevance of a whole-plant perspective when modeling plant
growth and regulation. The high coincidence between model calculations and measured values supports the notion that plant
acclimation can be both understood and predicted as a growth-optimizing mechanism.
Keywords:
dynamic optimization model, logarithmic growth, nitrogen uptake, starch accumulation, SLA, transient acclimation.
