Metabolism And Molecular Activities Of Cytokinins

In a number of recent biology meetings, plant growth factors have been a favorite topic. One may ask if a new colloquium devoted to the metab olism and the activities of cytokinins, considered at the molecular level, was really necessary and will add anything important to the previous contributions. As a matter of fact, the primary purpose of the organizers, of the French National Center of Scientific Research, and of the National In stitute of Agronomic Research which sponsored the colloquium was less the edition of a proceedings book than the desire to bring together a number of scientists who had made contributions towards solving prob· lems in cytokinin research and thereby to provide an opportunity for fruitful discussions without restrictions in the timetable. Indeed this primary target was attained. Moreover, important new fmdings and con clusions were presented by the participants that merited publication in the form ofthis book. It is beyond the scope of this foreword to adver tize or even to classify these new fmdings. We shall only mention a few of them. The reader will appreciate the contributions of those authors who worked hard to elucidate the biosynthetic pathways of natural cytokin ins.

In a number of recent biology meetings, plant growth factors have been a favorite topic. One may ask if a new colloquium devoted to the metab olism and the activities of cytokinins, considered at the molecular level, was really necessary and will add anything important to the previous contributions. As a matter of fact, the primary purpose of the organizers, of the French National Center of Scientific Research, and of the National In stitute of Agronomic Research which sponsored the colloquium was less the edition of a proceedings book than the desire to bring together a number of scientists who had made contributions towards solving prob· lems in cytokinin research and thereby to provide an opportunity for fruitful discussions without restrictions in the timetable. Indeed this primary target was attained. Moreover, important new fmdings and con clusions were presented by the participants that merited publication in the form ofthis book. It is beyond the scope of this foreword to adver tize or even to classify these new fmdings. We shall only mention a few of them. The reader will appreciate the contributions of those authors who worked hard to elucidate the biosynthetic pathways of natural cytokin ins.

Cytokinins are hormones involved in all aspects of plant growth and development and are essential for in vitro manipulation of plant cells and tissues. Much information has been gathered regarding the chemistry and biology of cytokinins, while recent studies have focused on the genetics and cytokinin-related genes. However, other than proceedings of symposia, no single volume on cytokinins has been written. This book is the first of its kind, homing in on the key subject areas of cytokinin-chemistry, biosynthesis, metabolism, activity, function, genetics, and analyses. These areas are comprehensively reviewed in individual chapters by experts currently active in the field. In addition, a personal history on the discovery of cytokinin is presented by Professor Folke Skoog. This volume summarizes previous findings and identifies future research directions.

Plant Hormones: Biosynthesis and Mechanisms of Action is based on research funded by the Chinese government’s National Natural Science Foundation of China (NSFC). This book brings a fresh understanding of hormone biology, particularly molecular mechanisms driving plant hormone actions. With growing understanding of hormone biology comes new outlooks on how mankind values and utilizes the built-in potential of plants for improvement of crops in an environmentally friendly and sustainable manner. This book is a comprehensive description of all major plant hormones: how they are synthesized and catabolized; how they are perceived by plant cells; how they trigger signal transduction; how they regulate gene expression; how they regulate plant growth, development and defense responses; and how we measure plant hormones. This is an exciting time for researchers interested in plant hormones. Plants rely on a diverse set of small molecule hormones to regulate every aspect of their biological processes including development, growth, and adaptation. Since the discovery of the first plant hormone auxin, hormones have always been the frontiers of plant biology. Although the physiological functions of most plant hormones have been studied for decades, the last 15 to 20 years have seen a dramatic progress in our understanding of the molecular mechanisms of hormone actions. The publication of the whole genome sequences of the model systems of Arabidopsis and rice, together with the advent of multidisciplinary approaches has opened the door to successful experimentation on plant hormone actions. Offers a comprehensive description of all major plant hormones including the recently discovered strigolactones and several peptide hormones Contains a chapter describing how plant hormones regulate stem cells Offers a fresh understanding of hormone biology, particularly molecular mechanisms driving plant hormone actions Discusses the built-in potential of plants for improvement of crops in an environmentally friendly and sustainable manner

Plant hormones play a crucial role in controlling the way in which plants growand develop. Whilemetabolism providesthepowerand buildingblocks for plant life, it is the hormones that regulate the speed of growth of the individual parts and integrate these parts to produce the form that we recognize as a plant. In addition, theyplayacontrolling role inthe processes of reproduction. This book is a description ofthese natural chemicals: how they are synthesizedand metabolized; howthey work; whatwe knowoftheir molecular biology; how we measure them; and a description ofsome ofthe roles they play in regulating plant growth and development. Emphasis has also been placed on the new findings on plant hormones deriving from the expanding use ofmolecular biology as a tool to understand these fascinating regulatory molecules. Even at the present time, when the role of genes in regulating all aspects of growth and development is considered of prime importance, it is still clear that the path of development is nonetheless very much under hormonal control, either via changes in hormone levels in response to changes in gene transcription, or with the hormones themselves as regulators ofgene transcription. This is not a conference proceedings, but a selected collection ofnewly written, integrated, illustrated reviews describing our knowledge of plant hormones, and the experimental work that is the foundation of this knowledge.

Plant hormones playa crucial role in controlling the way in which plants grow and develop. While metabolism provides the power and building blocks for plant life it is the hormones that regulate the speed of growth of the individual parts and integrate these parts to produce the form that we recognize as a plant. In addition, they playa controlling role in the processes of reproduction. This book is a description of these natural chemicals: how they are synthesized and metabolized; how they work; how we measure them; and a description of some of the roles they play in regulating plant growth and development. This is not a conference proceedings but a selected collection of newly written, integrated, illustrated reviews describing our knowledge of plant hormones and the experimental work which is the foundation of this knowledge. The information in these pages is directed at advanced students and professionals in the plant sciences: botanists, biochemists, molecular biologists, or those in the horticultural, agricultural and forestry sciences. It is intended that the book should serve as a text and guide to the literature for graduate level courses in the plant hormones, or as a part of courses in plant or comparative development. Scientists in other disciplines who wish to know more about the plant hormones and their role in plants should also find this volume invaluable It is hoped that anyone with a reasonable scientific background can find valuable information in this book expounded in an understandable fashion.

Phytohormone research is a crucially important area of plant sciences. Phytohormones are one of the key systems integrating metabolic and developmental events in the whole plant and the response of plants to external factors. Thus, they influence the yield and quality of crops. During the last decade we have slowly begun to understand the molecular mechanisms underlying phytohormone action, largely as a result of the rapid developments that have been made internationally in the field of plant molecular genetics. Putative receptor proteins for ethylene (1993- 95), brassinosteroids (1997) and cytokinins (2001) have been identified and the genes that encode them cloned. Primary response genes and elements of hormonal signal transduction have also been identified for most known phytohormones. There is now little doubt that phytohormones, like their animal counterparts, function as signal molecules and create a signalling network in the whole plant organism. The in vivo activity of hormones depends, among other things, on their rate of biosynthesis and metabolism, and on their transport into and out of target cells. Consequently, genes and enzymes involved in these processes are of particular interest. In recent years a number of genes encoding enzymes for the synthesis, modification and degradation of different phytohormones have been cloned and identified, as have genes encoding proteins involved in phytohormone transport and its regulation. Some classes of phytohormone have been shown to participate in stress reactions and can increase the resistance of plants to unfavorable environmental factors.