Functional convergence in plant responses to the environment.

Much comparative ecophysiological research has focused on contrasting species-specific behavior or ecological strategies with regard to regulation of basic physiological processes such as transpiration, photosynthesis and growth, leading to an emphasis on divergence rather than convergence in plant functioning. This review highlights selected examples in which substantial functional convergence among taxonomically, phylogenetically and architecturally diverse species has been revealed by applying appropriate scaling factors and identifying universal constraints or trade-offs. Recent empirical and theoretical scaling models emphasize the strong role that plant size, architecture, allometry and chemistry play in constraining functional traits related to water and carbon economy and growth. Taken together, the findings summarized here strongly suggest that there are a limited number of physiological solutions to a given problem of plant adaptation to the environment. Comparative ecophysiological studies will therefore benefit from consideration of the constraints that plant anatomical, structural and chemical attributes place on physiological functioning.