Photosynthesis

About: Photosynthesis is a research topic. Over the lifetime, 19789 publications have been published within this topic receiving 895197 citations.

Photosynthesis. Physical mechanisms and chemical patterns.

Abstract: Foreword Preface Part I. Research in Photosynthesis: Basic Developments to About 1960: 1. The chemical nature of photosynthesis 2. The roles of chlorophylls and other pigments 3. The cooperation of two quanta or two photosystems in photosynthesis 4. Major digression: molecular physics and spectroscopy quantum energy and redox energy measurements involving light Part II. Pigment-Protein Complexes in Photosynthetic Membranes: Their Compositions, Structures, and Functions: 5. Components of the photosynthetic membranes of bacteria: composition and function in energy transfer and photochemistry 6. Photosynthetic membranes of plants: components and their molecular organization energy transfer and its regulation 7. Measurements with polarized light: interactions of molecules in excited states orientations of pigments in photosynthetic tissues Part III. Photochemical Charge Separation, Secondary Transport of Electrons and Protons, and Oxygen Evolution: 8. Reaction centers: photochemical charge separation and interaction with nearest electron donors and acceptors 9. Oxygen evolution secondary transport of electrons and protons Part IV. The Formation of ATP and the Assimilation of Carbon Dioxide: 10. Electrochemical gradients and the formation of ATP 11. Carbon assimilation by plants Epilogue Notes Index.

Photosynthesis, respiration and water content in bryophytes

Abstract: Summary Response curves of photosynthesis to water content of bryophytes of dry habitats (e.g. Tortula intermedia, Camptothecium lutescens) show an optimum, with photosynthesis declining again at high water contents. Respiration may be stimulated by water stress, but is unaffected by high water contents. The steep portions of the photosynthesis and respiration curves lie within a similar range at low water contents. Some species of constantly moist habitats (e.g. Pellia epiphylla, Hookeria lucens) show photosynthesis increasing progressively to water contents of 500 to 1000 % of dry weight, and affected at much lower water deficits than respiration as the plant dries out. The response of photosynthesis and respiration to water potential is broadly similar in the two groups. In the species investigated there was generally measurable photosynthesis at –60 to – 100 bar, but little or none at – 150 to –200 bar. Respiration continues to somewhat lower water potentials of which the limits were not determined. Field measurements of the water content of shoots of five species over a period of 12 months showed much greater variation in Tortula muralis than in the woodland species. Maximum water contents in the field generally lay close to the optima of the photosynthesis response curves. The lower water contents recorded in these and in published data are considered in relation to sorption isotherms for bryophytes and other plant materials. The water associated with bryophyte shoots can be divided into (1) water within the cell walls (apoplast water), (2) water within the cytoplasm (symplast water), and (3) external capillary water. Changes in water content below about –200 bar take place chiefly within (1), between c.– 200 and c. - 2 bar within (2), and at higher water potentials chiefly within (3). Water movement within the shoots is physiologically important; the distribution and movement of water are mediated by the geometry of the capillary spaces of the cell walls and the plant surface. In species with papillose leaves, rates of capillary conduction in the interstices between the papillae are more than sufficient to balance evaporation. Conduction within the cell walls is likely to be important in species with non-papillose leaves, hut other pathways may also be involved, and water movement in these species requires further investigation.

Genomic basis for stimulated respiration by plants growing under elevated carbon dioxide

Abstract: Photosynthetic and respiratory exchanges of CO2 by plants with the atmosphere are significantly larger than anthropogenic CO2 emissions, and these fluxes will change as growing conditions are altered by climate change. Understanding feedbacks in CO2 exchange is important to predicting future atmospheric [CO2] and climate change. At the tissue and plant scale, respiration is a key determinant of growth and yield. Although the stimulation of C3 photosynthesis by growth at elevated [CO2] can be predicted with confidence, the nature of changes in respiration is less certain. This is largely because the mechanism of the respiratory response is insufficiently understood. Molecular, biochemical and physiological changes in the carbon metabolism of soybean in a free-air CO2 enrichment experiment were investigated over 2 growing seasons. Growth of soybean at elevated [CO2] (550 μmol·mol−1) under field conditions stimulated the rate of nighttime respiration by 37%. Greater respiratory capacity was driven by greater abundance of transcripts encoding enzymes throughout the respiratory pathway, which would be needed for the greater number of mitochondria that have been observed in the leaves of plants grown at elevated [CO2]. Greater respiratory quotient and leaf carbohydrate content at elevated [CO2] indicate that stimulated respiration was supported by the additional carbohydrate available from enhanced photosynthesis at elevated [CO2]. If this response is consistent across many species, the future stimulation of net primary productivity could be reduced significantly. Greater foliar respiration at elevated [CO2] will reduce plant carbon balance, but could facilitate greater yields through enhanced photoassimilate export to sink tissues.