SCALING SUN AND SHADE PHOTOSYNTHETIC ACCLIMATION OF ALOCASIA-MACRORRHIZA TO WHOLE-PLANT PERFORMANCE .2. SIMULATION OF CARBON BALANCE AND GROWTH AT DIFFERENT PHOTON FLUX DENSITIES

A whole-plant carbon balance model incorporating a light acclimation r esponse was developed for Alocasia macrorrhiza based on empirical data and the current understanding of light acclimation in this species. T he model was used to predict the relative growth rate (RGR) for plants that acclimated to photon flux density (PFD) by changing their leaf t ype, and for plants that produced only sun or shade leaves regardless of PFD. The predicted RGR was substantially higher for plants with sha de leaves than for those with sun leaves at low PFD. However, the pred icted RGR was not higher, and in fact was slightly lower, for plants w ith sun leaves than for those with shade leaves at high PFD. The decre ased leaf area ratios (LARs) of the plants with sun leaves counteracte d their higher photosynthetic capacities per unit leaf area (A(max)). The model was manipulated by changing parameters to examine the sensit ivity of RGR to variation in single factors. Overall, RGR was most sen sitive to LAR and showed relatively little sensitivity to variation in A(max) or maintenance respiration. Similarly, RGR was relatively inse nsitive to increases in leaf life-span beyond those observed. Respirat ion affected RGR only at low PFD, whereas A(max) was moderately import ant only at high PFD.