The possible role of reaction-diffusion in leaf shape

We consider mechanisms that may determine certain simple leaf shapes. Compa red with other aspects of plant morphogenesis, such as phyllotaxis or spira l leaf arrangement, rather little is known about leafshape-determining mech anisms. We develop mathematical models for the gross pattern of leaf shape based on reaction-diffusion sl systems. These models are consistent with wh at is known about factors that might determine leaf shape. They show that d iverse leaf shapes may be obtained from a single reaction-diffusion system. This has implications in terms of both convergent and divergent evolution. The models make predictions that can he tested experimentally. We predict the form of pre-patterns of growth promoters in leaf primordia of different sizes when the morphogens either diffuse into the primordia or are produce d locally We also predict the effects on leaf shape of removing parts of pr imordia at different times. The models can also predict the effects on leaf shape of the topical application of activators and inhibitors to leaf prim ordia.