Preface

Hormone crosstalk in plants For years, many plant science researchers who study the genetic programming that determines structural organization and reproductive processes self-identified as developmental biologists, while those studying plant responses to the environment identified as plant physiologists. Plant hormones such as auxins, cytokinins, and gibberellic acids that function as develop-mental messengers were viewed as functionally distinct from ‘stress ’ and ‘defence ’ hormones such as ethylene, abscisic acid, jasmonic acid, and salicylic acid. This division of hormone function was convenient, but was also known to be thoroughly artificial. Over the past two decades, new hormones have been identified, tissue and organ-specific hormone functions have been determined, methods have been developed to measure and visualize hormones in situ, receptor mechanisms have been conclusively identified or discounted, hormone transport processes have been largely elucidated, and the cellular processes downstream of hormone signalling have been painstakingly dissected. Over time, simple models of hormone antagonism (gibberellic acid vs. abscisic acid, auxin vs. cytokinin) have been displaced by the concept of complex hormonal crosstalk. The classification of hormones into developmental or environmental response categories has been replaced by mapping of hormonal signalling into transcriptional and post-transcriptional response net-works. This transition has accompanied a profound shift in the way that plant physiology and development are taught in the classroom, with undergraduate and graduate courses increasingly combining physiology and development as inseparabl