Recent studies that analyze the impact of various plant traits on whole-plant growth and competitive ability have provided insights into the selective pressures on characteristics such as leaf reflectivity, effective leaf size, stomatal conductance, size of photosynthetic enzyme pools, crown form, xylem structure, nitrogen fixation, and root versus shoot allocation. This research has reached an exciting stage, leading to quantitative predictions of favoured trends in these traits as a function of environmental parameters and fundamental physiological constraints. Such results reveal the...