SCALING MAXIMUM GROWTH-RATES ACROSS PHOTOSYNTHETIC ORGANISMS

1. This study provides evidence for the existence of general intrinsic patterns controlling the maximum growth rate of photosynthetic organi sms, based on a compilation of data from more than 120 reports, the sp ecies ranging from unicellular algae to trees and thick-leaved desert plants. 2. We used thickness and nutrient concentration of the photosy nthetic tissue to scale differences in maximum growth rate among plant s, based on the demonstrated importance of these plant traits in regul ating the maximum growth rates of particular plant groups. 3. The grow th rate declined with increasing thickness of the photosynthetic struc tures and increased with increasing nitrogen and phosphorus concentrat ion. The strong dependence of growth rate and nutrient concentrations on tissue thickness reflect broad-scale patterns and not the adaptive response of individual or closely related species of similar tissue th ickness to varying environmental conditions. 4. The scaling of maximum growth rate is similar to the scaling of metabolic rate to animal siz e. Thickness of the photosynthetic structures therefore plays an impor tant role in the environmental control of plant performance and evolut ion, setting thresholds for the growth and productivity of photosynthe tic organisms.