Abstract

Plants exhibit a striking diversity of forms and structures, which are difficult to interpret. The functional approach to the study of plant form emerged as a separate discipline at the beginning of the twentieth century with the first classifications of growth forms in relation to climate and with tentative ecophysiological studies of plant responses to the environment (Waller 1986). Physiological ecology now makes detailed predictions on how physical and physiological characteristics affect plant photosynthesis, whereas plant population ecology translates patterns of growth into fitness of individuals and populations. And plant structure remains an essential tool for all these exercises of interpreting plant performance in natural habitats and for scaling from cellular and leaf-level to ecosystem processes (Ehleringer and FIeld 1993). Plant performance can be understood as the crucial link between its phenotype and its ecological success and the form becomes ecologically and evolutionary relevant when it affects performance (Koehl 1996). It is important to consider that misconceptions can arise from studies in which selective advantages of particular structures are not made with a mechanistic understanding of how the structural traits affect performance. Koehl (1996) showed that the relationship between morphology and performance can be nonlinear, context-dependent, and sometimes surprising. Remarkably, new functions and novel ecological consequences of morphological changes can arise simply as the result of changes in size or habitat.