Biotic and abiotic consequences of differences in leaf structure

Both within and between species, leaves of plants display wide ranges in st ructural features. These features include: gross investments of carbon and nitrogen substrates (e.g. leaf mass per unit area); stomatal density, distr ibution between adaxial and abaxial surfaces, and aperture; internal and ex ternal optical scattering structures; defensive structures, such as trichom es and spines; and defensive compounds, including UV screens, antifeedants, toxins, and silica abrasives. I offer a synthesis of selected publications , including some of my own. A unifying theme is the adaptive value of expre ssing certain structural features, posed as metabolic costs and benefits, f or (1) competitive acquisition and use of abiotic resources (such as water, light and nitrogen) and (2) regulation of biotic interactions, particularl y fungal attack and herbivory. Both acclimatory responses in one plant and adaptations over evolutionary time scales are covered where possible. The u biquity of trade-offs in function is a recurrent theme; this helps to expla in diversity in solutions to the same environmental challenges but poses pr oblems for investigators to uncover numerous important trade-offs. I offer some suggestions for research, such as on the need for models that integrat e biotic and abiotic effects (these must be highly focused), and some specu lations, such as on the intensity of selection pressures for these structur es.