Cellular differentiation and leaf morphogenesis in Arabdopsis

A focused approach that exploits a single plant species, namely, Arabidopsi s thaliana, as a means to understand how leaf cells differentiate and the f actors that govern overall leaf morphogenesis has begun to generate a signi ficant body of knowledge in this model plant. Although many studies have co ncentrated on specific cell types and factors that control their differenti ation, some degree of consensus is starting to be reached. However, an unde rstanding of specific mechanisms by which cells differentiate in relation t o their position, that appears to be an overriding factor in this process, is not yet in place for cell types in the Arabidopsis leaf. It is clear tha t perturbations in cellular development within the leaf do not necessarily have a general effect on morphogenesis. Environmental factors, particularly light, have been known to affect leaf cell differentiation and expansion, and endogenous hormones also appear to play an important role, through mech anisms that are beginning to be uncovered. It is likely that continued iden tification of genes involved in leaf development and their regulation in re lation to positional information or other cues will lead to a clearer under standing of the control of differentiation and morphogenesis in the Arabido psis leaf.