UCLA

Leaf structure and function is important in driving ecosystem fluxes, tolerance of environmental stressors, species distributions and climate change responses, with applications for agricultural breeding and engineering. Yet, the interface of leaf hydraulic structure and function with the spatial and temporal aspects of developmental processes has largely been unexplored across species. Such a pursuit has the power to provide deep insight into the drivers and constraints on the evolution of physiological adaptation. In this dissertation, I leverage developmental processes to gain insight into how diverse hydraulic mechanisms arise, how developmental constraints influence environmental adaptation, how allometric relationships among cell and tissue anatomy and leaf size arise, and how leaf economics are linked with leaf expansion processes. For three of these chapters, I focus on diverse grasses, and demonstrate that grass leaf size is critical trait for climate adaptation globally, due to developmental constraints between leaf growth and venation, C3 and C4 grasses evolved some similar but also differential leaf cell, tissue and morphological allometries, and C3 and C4 grasses evolved contrasting hydraulic adaptations that underlie their differential climate adaptation. For two chapters, I focus on diverse eudicot species, and show the developmental bases for leaf trichome and stomatal densities for trichomous species and how their developmental processes allow for positive coordination across species, and the developmental determinants underlying leaf size and how leaf expansion processes are coordinated with the leaf economics spectrum. This work highlights the importance of incorporating developmental processes to better understand the evolutionary ecology of leaf structure and function, and will provide critical avenues for predicting responses to climate change and applications for agriculture