Photosynthesis II

M. GIBBS and E. LATZKO In the preface to his Experiments upon Vegetables, INGEN-Housz wrote in 1779: "The discovery of Dr. PRIESTLEY that plants have a power of correcting bad air . . . shows . . . that the air, spoiled and rendered noxious to animals by their breath­ ing in it, serves to plants as a kind of nourishment. " INGEN-Housz then described his own experiments in which he established that plants absorb this "nourishment" more actively in brighter sunlight. By the turn of the eighteenth century, the "nourishment" was recognized to be CO . Photosynthetic CO2 assimilation, the 2 major subject of this encyclopedia volume, had been discovered. How plants assimilate the CO was a question several successive generations 2 of investigators were unable to answer; scientific endeavor is not a discipline in which it is easy to "put the cart before the horse". The horse, in this case, was the acquisition of radioactive isotopes of carbon, especially 14c. The cart which followed contained the Calvin cycle, formulated by CALVIN, BENSON and BASSHAM in the early 1950's after (a) their detection of glycerate-3-P as the first stable product of CO fixation, (b) their discovery, and that by HORECKER 2 and RACKER, of the COz-fixing enzyme RuBP carboxylase, and (c) the reports by GIBBS and by ARNON of an enzyme (NADP-linked GAP dehydrogenase) capable of using the reducing power made available from sunlight (via photo­ synthetic electron transport) to reduce the glycerate-3-P to the level of sugars.

Contenu

I. Introduction.- II. CO2 Assimilation.- II A. The Reductive Pentose Phosphate Cycle.- 1. The Reductive Pentose Phosphate Cycle and Its Regulation.- A. Introduction.- B. The Reductive Pentose Phosphate Cycle.- I. The Cyclic Path of Carbon Dioxide Fixation and Reduction.- II. Individual Reactions of the RPP Cycle.- III. Stoichiometry and Energetics.- C. Utilization of the Products of the RPP Cycle.- I. Starch Synthesis.- II. Triose Phosphate Export.- III. Glycolate Formation.- D. Mapping the RPP Cycle.- I. Early History.- II. First Products of CO2 Fixation.- III. Sugar Phosphates.- IV. Studies of Light-Dark and High-Low CO2 Transients.- V. Discovery of Enzymes of the RPP Cycle.- E. Metabolic Regulation of the RPP Cycle.- I. In Vivo Kinetic Steady-State Studies with Labeled Substrates.- II. Light-Dark Regulation.- III. Regulation of the RPP Cycle During Photosynthesis.- F. Concluding Remarks.- References.- 2. The Isolation of Intact Leaf Cells, Protoplasts and Chloroplasts.- A. Introduction.- B. Isolation of Plant Leaf Cells and Protoplasts.- I. Mechanical Methods.- II. Enzymic Methods.- III. Cell and Protoplast Isolation from C3 and C4 Grasses.- C. Isolation of Intact Chloroplasts.- I. Plant Material and Media.- II. Isolation Methods.- III. Chloroplast Isolation from Other Plants.- References.- 3. Studies with the Reconstituted Chloroplast System.- A. Reconstituted Chloroplast Systems.- I. Introduction.- II. Definition.- III. Methods of Preparation.- IV. Activities Achieved.- V. Advantages and Drawbacks.- B. Factors Affecting the Activity of Partial Reaction Sequences in Reconstituted Chloroplast Systems.- I. The Light Reactions.- II. The Conversion of 3-Phosphoglycerate to Triose Phosphate.- III. The Conversion of Triose Phosphate to Pentose Phosphate.- IV. The Conversion of Ribulose-5-Phosphate to Ribulose-1, 5-Bisphosphate.- V. The Fixation of Carbon Dioxide.- VI. Autocatalysis.- C. Reconstituted Chloroplast Systems and the Regulation of Photosynthesis.- I. The Role of Magnesium, pH and Reductants.- II. The Role of the ATP/ADP Ratio.- References.- 4. Autotrophic Carbon Dioxide Assimilation in Prokaryotic Microorganisms.- A. Introduction.- B. Principles of Autotrophic Carbon Dioxide Assimilation in Prokaryotic Cells.- C. The Pathway of Carbon Dioxide Assimilation in Green Sulfur Bacteria.- D. The Pathway of Carbon Dioxide Assimilation in Purple Bacteria.- E. The Pathway of Carbon Dioxide Assimilation in Blue-Green Algae.- F. The Pathway of Carbon Dioxide Assimilation in Chemolithotrophic Bacteria.- G. Regulatory Aspects of Carbon Dioxide Assimilation in Prokaryotic Microorganisms.- References.- 5. Light-Enhanced Dark CO2 Fixation.- A. Light-Enhanced Dark CO2 Fixation in C3 Plants.- I. Introduction.- II. Capacity for Light-Enhanced Dark CO2 Fixation.- III. Products.- IV. RuBP, NADPH, and ATP Levels.- V. Fate of PGA.- VI. Higher Plants.- B. Light-Enhanced Dark CO2 Fixation in C4 Plants.- References.- II B. The C4 and Crassulacean Acid Metabolism Pathways.- 6. The C4 Pathway and Its Regulation.- A. Discovery of C4 Photosynthesis.- B. Kranz Leaf Anatomy.- I. Variations in Leaf Anatomy.- C. Environmental Regulation of C4 Photosynthesis.- I. Light Intensity.- II. CO2 Concentration.- III. O2 Concentration.- IV. Temperature.- V. Water.- VI. Salinity.- VII. Nitrogen Supply.- D. Biochemical Schemes for the C4 Pathway.- E. Regulation via Enzymatic and Metabolic Compartmentation into Leaf Cell Types.- F. Efficiency of C4 Leaf Photosynthesis.- I. CO2 Pools.- II. CO2 Trapping.- III. CO2 Fixation by Bundle Sheath Cells.- G. C3-C4 Intermediate Plants.- H. Criteria for the Presence of C4 Photosynthesis.- I. Conclusions in the Regulation of C4 Photosynthesis in Leaves.- References.- 7. C4 Metabolism in Isolated Cells and Protoplasts.- A. Introduction.- B. Three Groups of C4 Plants.- C. Localization of Enzymes of C4 Metabolism in C4 Plants.- I. Intercellular Localization.- II. Intracellular Localization.- D. Criteria for Intactness of Cellular Preparations.- I. Mesophyll Preparations.- II. Bundle Sheath Preparations.- E. Variations in C4 Metabolism.- I. Mesophyll Cells of C4 Plants.- II. Bundle Sheath Cells of C4 Plants.- F. Energetics in C4 Metabolism.- G. Future Studies on C4 Metabolism with Cells and Protoplasts.- I. Transport Studies.- II. Screening for Inhibitors of C4 Photosynthesis.- References.- 8. The Flow of Carbon in Crassulacean Acid Metabolism (CAM).- A. Introduction.- B. Basic Phenomena of CAM.- C. The Metabolic Sequences of CAM.- I. The Flow of Carbon During the Night.- II. The Flow of Carbon During the Day.- D. Regulation of Carbon Flow in CAM.- E. Conclusions.- References.- 9. CAM: Rhythms of Enzyme Capacity and Activity as Adaptive Mechanisms.- A. Introduction.- B. Endogenous Versus Nonendogenous Rhythms: A Necessary Distinction.- C. Enzyme Capacity and Enzyme Activity: Two Distinct Levels of Control.- D. Rhythms Connected with CAM.- I. Components of the Malate Rhythm.- II. CO2 Uptake and CO2 Output.- III. PEP Carboxylase.- IV. Malate Dehydrogenase.- V. Malic Enzyme (NADP).- VI. Aspartate Aminotransferase.- VII. Enzymes of the Glycolytic Pathway.- VIII. Tricarboxylic Acid Cycle.- E. Working Hypothesis and Models.- I. Seasonal Adaptation.- II. Timing CAM.- References.- 10. ?13C as an Indicator of Carboxylation Reactions.- A. Introduction.- B. Carbon Isotope Fractionation and Its Measurement.- C. Variation in ?13C Values Between Plants.- I. Discrimination Caused by the Photosynthetic Pathway.- II. Variation in ?13C Values Between Plant Varieties and Species.- III. Variation in ?13C Values Within a Plant.- IV. Fractionation Associated with Carboxylation Enzymes.- V. Compartmental Organisation and Isotope Fractionation.- VI. Respiration.- D. Environmental Effects on the ?13C Value of Plants.- I. Temperature.- II. Carbon Dioxide Concentration.- III. Oxygen Concentration Effects on Discrimination.- IV. Light Level.- V. Availability of Water.- VI. Salinity and Carbon Isotope Fractionation.- E. Implications of Variation in ?13C Values Among Plant Species.- I. Natural Products.- II. Paleoecology.- III. Physiology - Plant, Animal, and Human.- F. Conclusions.- References.- II C. Factors Influencing CO2 Assimilation.- 11. Interactions Between Photosynthesis and Respiration in Higher Plants.- A. Introduction.- I. The Relevance of Photosynthetic and Respiratory Interactions.- B. Physiological Observations.- I. Plants with C3-Type Photosynthesis.- II. Plants wi…