The discovery of the reversible red far-red control of plant growth and development and the subsequent in vivo identification and isolation of the photoreceptor pigment, phyto chrome, constitutes one of the great achievements in modern biology. It was primarily a group of investigators at the Plant Industry Station, Beltsville, Mary land, headed by the botanist H.A. BORTHWICK and the physical chemist S.B. HENDRICKS, who made the basic discoveries and developed a theoretical framework on which the current progress in the field of phytochrome is still largely based. While the earlier development of the phytochrome concept has been covered by a num ber of excellent articles by the original investigators [104,105,33,238] as well as by others who joined the field of phytochrome research later [72, 109, 219], a comprehensive and up-to-date treatment of photomorphogenesis is not available at present. Since it seems to be needed for teaching as well as for researchers I have tried to summarize the present state of the field, reviewing the historical aspects of the phytochrome story only insofar as they are required to understand the present situation. The emphasis of my treatment will be on developmental physiology ("photomorphogenesis") rather than on phytochrome per se. Front Matter....Pages I-IX Phenomenology of Photomorphogenesis; the Goals of Photomorphogenic Research; the Operational Criteria for the Involvement of Phytochrome....Pages 1-12 Some Properties of Phytochrome....Pages 13-23 Intracellular Localization of Phytochrome....Pages 24-36 Induction Experiments Versus Steady State Experiments; the Problem of the “High Irradiance Response” (HIR)....Pages 37-47 Phytochrome and the Diversity of Photoresponses; “Positive” and “Negative” Photoresponses; a Unifying Hypothesis....Pages 48-59 Phytochrome-mediated Enzyme Induction....Pages 60-68 Enzyme Repression, Mediated by Phytochrome through a Threshold Mechanism....Pages 69-76 Phytochrome-mediated Modulation of Metabolic Steady States and of Photonastic Movements....Pages 77-87 Control of Longitudinal Growth by Phytochrome....Pages 88-97 Modulation of Hypocotyl Longitudinal Growth by P fr (ground state) through a Threshold Mechanism....Pages 98-104 The Problem of the Primary Reaction of Phytochrome....Pages 105-117 Interaction between Phytochrome and Hormones....Pages 118-124 The Double Function of Phytochrome in Mediating Anthocyanin and Enzyme Synthesis....Pages 125-131 Repression of Lipoxygenase Synthesis by P fr : The Problem of Primary and Secondary Differentiation....Pages 132-140 Light-mediated Flavonoid Synthesis: A Biochemical Model System of Differentiation....Pages 141-148 Control of Distinct Enzymes (PAL, AO) in Different Organs of a Plant (Mustard Seedling)....Pages 149-152 Energetics of Morphogenesis....Pages 153-156 Control of Plastogenesis by Phytochrome....Pages 157-177 Phytochrome and Flower Initiation....Pages 178-184 Phytochrome and Seed Germination....Pages 185-189 Examples of Blue-light-mediated Photomorphogenesis....Pages 190-204 The Problem of Phototropism....Pages 205-209 Genes and Environment....Pages 210-215 Epilogue: Science and Responsibility....Pages 216-226 Back Matter....Pages 227-240
