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Showing papers on "Photosynthesis published in 1980"


Journal ArticleDOI
01 Jun 1980-Planta
TL;DR: Various aspects of the biochemistry of photosynthetic carbon assimilation in C3 plants are integrated into a form compatible with studies of gas exchange in leaves.
Abstract: Various aspects of the biochemistry of photosynthetic carbon assimilation in C3 plants are integrated into a form compatible with studies of gas exchange in leaves. These aspects include the kinetic properties of ribulose bisphosphate carboxylase-oxygenase; the requirements of the photosynthetic carbon reduction and photorespiratory carbon oxidation cycles for reduced pyridine nucleotides; the dependence of electron transport on photon flux and the presence of a temperature dependent upper limit to electron transport. The measurements of gas exchange with which the model outputs may be compared include those of the temperature and partial pressure of CO2(p(CO2)) dependencies of quantum yield, the variation of compensation point with temperature and partial pressure of O2(p(O2)), the dependence of net CO2 assimilation rate on p(CO2) and irradiance, and the influence of p(CO2) and irradiance on the temperature dependence of assimilation rate.

7,312 citations


Journal ArticleDOI
TL;DR: A comparison of plants from contrasting thermol regimes in Thermally Contrasting Climates and adoptive responses in the heat stability 0/ the photosynthetic apparatus highlights the need to understand more fully the role of photosynthesis in climate change.
Abstract: INTRODUCTION 492 ECOLOGICAL ASPECTS OF PHOTOSYNTHETIC TEMPERATURE ADAPTATION 493 Photosynthetic Temperature Dependence in Thermally Contrasting Climates ........ 493 Photosynthetic Temperature Acclimation 497 Seasonal acclimation in natural habitats ...... ....... 497 Studies in controlled environments 499 THE MECHANISTIC BASIS FOR PHOTOSYNTHETIC RESPONSE AND ADAPTATION TO TEMPERATURE 504 Reversible Temperature Respon.ses 505 Stomata! effec� o� the . temJH!.rature response 0/ photo.rynthesis ......... ....... 505 Interacttons with /lght mtenslty 507 C, photo.rynthesis (lM photorespiration 507 C, photo.rynthesis 515 Comparison 0/ plants from contrasting thermol regimes ...... ...... 517 ["eversible Temperature Respon.ses 519 Low temperature sensitMty ....... 519 High temperature sensitivity 524 Adoptive responses in the heat stability 0/ the photosynthetic apparatus 530 CONCLUDING REMARKS 532

2,779 citations


Journal ArticleDOI
31 Jul 1980-Nature
TL;DR: In this paper, the authors showed that the irradiation of the carbohydrates, not only sugar or starch but also cellulose, in the presence of water and a RuO2/TiO 2/Pt photocatalyst powder leads to the efficient production of hydrogen gas.
Abstract: Attempts have been made to find green plants which produce low-molecular weight hydrocarbons1,2 and to find seaweeds which produce hydrogen from water utilizing solar energy3,4. These attempts are aimed at finding methods of making use of the photosynthetic process in plants for direct production. Most green plants, however, synthesize carbohydrates, such as sugar, starch and/or cellulose, from water and carbon dioxide. The C4 plants5, such as corns and sugar cane, grow rapidly, utilizing solar energy with ∼1% efficiency for the fixation of CO2. This value is 10 times larger than that of the average efficiency of photosynthesis of plants, 0.1%. However, the carbohydrates produced by these plants cannot be used directly as fuel. Here we show a new route for the conversion of carbohydrates into hydrogen (a clean fuel in the hydrogen energy system), taking advantage of the photocatalytic process. We found that the irradiation of the carbohydrates, not only sugar or starch but also cellulose, in the presence of water and a RuO2/TiO2/Pt photocatalyst powder leads to the efficient production of hydrogen gas.

552 citations


Journal ArticleDOI
TL;DR: The possibility of using Fe stress as an experimental tool in the study of limiting factors was explored and it is suggested that the effect of Fe stress may be sufficiently specific for it to be used for the control and study of photochemical capacity in vivo.
Abstract: The possibility of using Fe stress as an experimental tool in the study of limiting factors was explored Results show that Fe stress decreased the chlorophyll (Chl) a, Chl b, carotene, and xanthophyll content of leaves of sugar beets (Beta vulgaris L) and that the maximum rate of photosynthetic CO(2) uptake (P(max)) per unit area was linearly related to Chl (a + b) per unit area Measurements of noncyclic ATP formation by isolated chloroplasts at light saturation indicate that photosynthetic electron transport capacity decreased concomitantly with pigment content under Fe stressIron stress decreased Chl per chloroplast but had no effect on the number of leaf cells per unit area, average leaf cell volume, number of chloroplasts per unit area, or leaf soluble protein per unit area Average chloroplast volume, protein N per chloroplast, and ribulose bisphosphate carboxylase activity were diminished by Fe stress but to a lesser extent than Chl per chloroplast The reduction in pigment concentration with Fe stress led to a relatively small decrease in light absorption, the fraction of incident light absorbed remaining high (49%) even at very low leaf Chl contents There was no apparent change in the quantum yield of attached leaves at low irradiances, but at high irradiances, the capacity to convert absorbed light to chemical energy was greatly diminished in Fe-stressed leavesTHE RESULTS SUGGEST: (a) that P(max) per unit area are decreased linearly with Chl per unit area because of a decrease in photochemical capacity rather than a change in light absorption; and (b) that the effect of Fe stress may be sufficiently specific for it to be used as an experimental tool for the control and study of photochemical capacity in vivo

323 citations


Journal ArticleDOI
TL;DR: The principal symptom of cadmium action was the occurrence of large plastoglobules and a disorganization of the lamellar structure, mainly grana stacks, which caused grana stacking and restoration of photosystem II activity.
Abstract: Tomato plants (Lycopersicum esculentum Mill. cv. Moneymaker) grown on nutrient medium containing cadmium exhibit reduced net photosynthesis and reduced contents of chlorophyll and accessory pigments. In chloroplasts isolated from cadmiumtreated plants photosystem II activity, as measured by 2,6-dichlorophenolindophenol photoreduction, and photosystem II + I activity (H2O methyl viologen) were both inhibited to about 60%. When 1,5-diphenylcarbazide was used as artificial electron donor, no significant cadmium effect was observed. Photosystem I activity was not affected by cadmium. The fine structure of chloroplasts in cadmium-treated plants was degenerated, similarly to senescence response. The principal symptom of cadmium action was the occurrence of large plastoglobules and a disorganization of the lamellar structure, mainly grana stacks. Transfer of cadmium-treated plants into a medium with increased manganese level caused grana stacking and restoration of photosystem II activity.

323 citations



Journal ArticleDOI
01 Aug 1980-Planta
TL;DR: Measurements of the kinetics of Cinorg transport indicate that the affinity of the transport mechanism for CInorg is similar in both high- and low-CO2-grown cells, however, Vmax is 10-fold higher in the latter case, and it is suggested that this higher Vmax for transport is the basis of the superior capability to accumulate Cinorge and the higher apparent photosynthetic affinity for external Cinborg in low- CO2- grown Anabaena.
Abstract: The apparent photosynthetic affinity of A. variabilis to CO2 is greatly affected by the CO2 concentration in the medium during growth. Halfmaximal rate of photosynthetic O2 evolution is achieved at 10 μM and 100 μM inorganic carbon (Cinorg) in cells grown at low-CO2 (air) and high CO2 (5% v/v CO2 in air), respectively, whilst the maximum rate of photosynthesis is similar in both cases. Both high- and low-CO2-grown Anabaena accumulate Cinorg within the cell; however, the rate of accumulation and the steady-state internal Cinorg concentration reached is much higher in low as compared with high-CO2-grown cells. It is suggested that Anabaena cells actively accumulate Cinorg. Measurements of the kinetics of Cinorg transport indicate that the affinity of the transport mechanism for Cinorg is similar (Km(Cinorg(≃150 μM) in both high- and low-CO2-grown cells. However, Vmax is 10-fold higher in the latter case. It is suggested that this higher Vmax for transport is the basis of the superior capability to accumulate Cinorg and the higher apparent photosynthetic affinity for external Cinorg in low-CO2-grown Anabaena. Carbonic anhydrase activity was not detectable in Anabaena, yet both photosynthetic affinity to Cinorg in the medium (but not Vmax) and the rate of accumulation of Cinorg were inhibited by the carbonic-anhydrase inhibitor ethoxyzolamide.

285 citations


BookDOI
01 Jan 1980
TL;DR: The Biological Significance and Evolution of Photosensory Systems and the Nature of the Blue Light Photoreceptor are still an Open Question.
Abstract: Reviews on Various Fields of Blue Light Action.- The Biological Significance and Evolution of Photosensory Systems.- Short Wavelength Light in Invertebrate Visual Sense Cells - Pigments, Potentials and Problems.- Bacteriorhodopsin and its Position in the Blue Light Syndrome.- Chemical Modification of Bacteriorhodopsin by Phenylisothiocyanate: Effect on the Photocycle.- Effects of Blue Light on Movement of Microorganisms.- Blue Light-Induced Intracellular Movements.- Phytochrome and Non-Phytochrome Dependent Blue Light Effects on Intracellular Movements in Fresh-Water Algae.- Interaction Between Blue Light and Phytochrome in Photomorphogenesis.- Sensory Transduction in Phycomyces Photoresponses.- Regulation of Cell Growth and Cell Cycle by Blue Light in Adiantum Gametophytes.- Blue Light and Transcription.- Photoreceptors and Primary Reactions.- Spectroscopic and Photochemical Characterization of Flavoproteins and Carotenoproteins as Blue Light Photoreceptors.- Carotenoids as Primary Photoreceptors in Blue-Light Responses.- On the Nature of the Blue Light Photoreceptor: Still an Open Question.- Conformational Changes Caused by Blue Light.- Interactions of Flavins with Cytochrome C and Oxygen in Excited Artificial Systems.- Artificial Flavin/Membrane Systems a Possible Model for Physiological Blue Light Action.- Effects of UV and Blue Light on the Bipotential Changes in Etiolated Hypocotyl Hooks of Dwarf Beans.- Blue Light-Controlled Conidiation and Absorbance Change in Neurospora are Mediated by Nitrate Reductase.- Phototropism in Phycomyces: a Photochromic Sensor Pigment?.- Blue and Near Ultraviolet Reversible Photoreaction in Conidial Development of Certain Fungi.- Blue Light Responses in the Siphonaceous Alga Vaucheria.- Cis to Trans Photoisomerization of ?-Carotene in Euglena gracilis Var. bacillaris W3BUL: Further Purification and Characterization of the Photoactivity.- Carotenogenesis.- Blue Light-Induced Carotenoid Biosynthesis in Microorganisms.- Photokilling and Protective Mechanisms in Fusarium aquaeductuum.- Dose Response and Related Aspects of Carotenogenesis in Neurospora crassa.- Carbon Metabolism and Respiration.- Effects of Blue Light on Respiration and Non-Photosynthetic CO2 Fixation in Chlorella vulgaris 11h Cells.- Effect of Blue Light on CO2 Fixation in Heterotrophically Grown Scenedesmus obliquus Mutant C-2A'.- Light-Induced Carbon Metabolism in an Early Stage of Greening in Wild Type and Mutant C-2A' Cells of Scenedesmus obliquus.- Enhancement of Carbohydrate Degradation by Blue Light.- Blue Light-Effects on Enzymes of the Carbohydrate Metabolism in Chlorella. 1. Pyruvate Kinase.- Blue Light-Effects on Enzymes of the Carbohydrate Metabolism in Chlorella. 2. Glyceraldehyde 3-Phosphate Dehydrogenase (NADP-Dependent).- Blue Light-Induced Enhancement in Activity of Certain Enzymes in Heterotrophically Grown Cultures of Scenedesmus obliquus.- Effect of 360 nm Light on RuBPCase Products in Vitro - Role of Copper in the Reaction.- The Photoinactivation of Micro-Algal Ribulose Bisphosphate Carboxylase its Physiological and Ecological Significance.- A Rhythmic Change in the Enhancement of the Dark Respiration of Chlorella fusca Induced by a Short Blue-Light Exposure of Low Intensity.- Interaction Between Blue Light and Nitrogen Metabolism.- Regulation by Monochromatic Light of Nitrate Uptake in Chlorella fusca.- Flavin-Mediated Photoreduction of Nitrate by Nitrate Reductase of Higher Plants and Microorganisms.- Effects of Ammonia on Carbon Metabolism in Photosynthesizing Chlorella vulgaris 11 h: the Replacement of Blue Light by Ammonium Ion.- Comparative Studies on the Effect of Ammonia and Blue Light on the Regulation of Photosynthetic Carbon Metabolism in Higher Plants.- The Effect of Blue and Red Light on the Content of Chlorophyll, Cytochrome f, Soluble Reducing Sugars, Soluble Proteins and the Nitrate Reductase Activity During Growth of the Primary Leaves of Sinapis alba.- Chloroplast Development.- Blue Light Effects on Plastid Development in Higher Plants.- Blue Light-Induced Development of Thylakoid Membranes in Isolated Seedling Roots and Cultured Plant Cells.- The Effect of Light Quality and the Mode of Illumination on Chloroplast Development in Etiolated Bean Leaves.- The Importance of Blue Light for the Development of Sun-Type Chloroplasts.- Blue Light and the Photocontrol of Chloroplast Development in Euglena.- Effects of Blue Light on Greening in Microalgae.- Blue Light Regulation of Chloroplast Development in Scenedesmus Mutant C-2A'.- The Action of Blue Light on 5-Aminolevulinic Acid Formation.- Physiology of Blue Light Effects.- Blue-Light Photomorphogenesis in Mushrooms (Basidiomycetes).- Blue Light Induced Differentiation in Phycomyces blakesleeanus.- Effect of Blue Light on Metabolic Processes, Development and Movement in True Slime Molds.- Blue-Light Photoreception in the Inhibition and Synchronization of Growth and Transport in the Yeast Saccharomyces.- Role of Light at Shorter Wavelength in Photobiological Phenomena in Blue-Green Algae.- Blue Light Effects on Some Algae Collected from Subsurface Chlorophyll Layer in the Western Pacific Ocean.- Visible and Spectrophotometrically Detectable Blue Light Responses of Maize Roots.- Synergistic Action of Red and Blue Light on Stomatal Opening of Vicia faba Leaves.- The Blue Light Response of Stomata and the Green Vacuolar Fluorescence of Guard Cells.- Light Induced Changes in the Centrifugability of Chloroplasts Mediated by an Irradiance Dependent Interaction of Respiratory and Photosynthetic Processes.- Growth Rate Patterns Which Produce Curvature and Implications for the Physiology of the Blue Light Response.- Organism Index.

255 citations


Journal ArticleDOI
TL;DR: The evidence strongly suggests that HCO(3) (-) was a direct C source for photosynthesis and serves to raise the CO(2) concentration around the carboxylase to levels high enough for effective fixation.
Abstract: The possibility of HCO 3 − transport in the blue-green alga (cyanobacterium) Coccochloris peniocystis has been investigated. Coccochloris photosynthesized most rapidly in the pH range 8 to 10, where most of the inorganic C exists as HCO 3 − . If photosynthesis used only CO 2 from the external solution the rate of photosynthesis would be limited by the rate of HCO 3 − dehydration to CO 2 . Observed rates of photosynthesis at alkaline pH were as much as 48-fold higher than could be supported by spontaneous dehydration of HCO 3 − in the external solution. Assays for extracellular carbonic anhydrase were negative. The evidence strongly suggests that HCO 3 − was a direct C source for photosynthesis. Weakly buffered solutions became alkaline during photosynthesis with a one-to-one stoichiometry between OH − appearance in the medium and HCO 3 − initially added. Alkalization occurred only during photosynthesis and was blocked by 3-(3,4-dichlorophenyl)-1, 1-dimethylurea, diuron. It is suggested that HCO 3 − was transported into cells of Coccochloris in exchange for OH − produced as a result of HCO 3 − fixation in photosynthesis. The inorganic C concentration required to support a rate of photosynthesis of half the maximum rate ( K m ) was 6 micromolar at pH 8.0 or, in terms of available CO 2 , a K m of 0.16 micromolar. This value is two orders of magnitude lower than reported K m values for the d-ribulose-1,5-bisphosphate carboxylase for blue-green algae. It is suggested that the putative HCO 3 − transport by Coccochloris serves to raise the CO 2 concentration around the carboxylase to levels high enough for effective fixation.

251 citations


Journal ArticleDOI
TL;DR: Although loss of RuBPCase probably is the primary event responsible for the decline in photosynthesis during leaf senescence, other factors such as in vivo regulation and stomatal aperture must also be considered.
Abstract: The relationship between loss of ribulose-1,5-bisphosphate carboxylase (RuBPCase) and the decline in photosynthesis during the senescence of barley primary leaves was assessed. Loss of RuBPCase accounted for about 85% of the decrease in soluble protein. RuBPCase was highly correlated with in vitro RuBPCase activity (r = 0.95) and gross photosynthesis (r = 0.96). However, the rate of photosynthesis per milligram RuBPCase increased during the early stages of leaf senescence. The concentration of nonreducing sugars was negatively correlated (1% level) with photosynthesis. Free α-amino N, in contrast to nonreducing sugars, declined markedly during senescence. A decrease in chlorophyll and an increase in in vitro protease activity was observed, but these changes did not appear to be closely related to the decline in photosynthesis and RuBPCase. Mesophyll resistance increased at the same rate that photosynthesis and RuBPCase declined. Stomatal resistance increased more rapidly than mesophyll resistance and accounted for about 24% of the total increase in resistance to CO2 diffusion. The concentration of CO2 in the intercellular air spaces decreased during the last stage of senescence. Although loss of RuBPCase probably is the primary event responsible for the decline in photosynthesis during leaf senescence, other factors such as in vivo regulation and stomatal aperture must also be considered.

220 citations


Journal ArticleDOI
TL;DR: The effect of Fe stress on photosynthetic unit number, size, and composition was investigated by measuring P(700), cytochrome (Cyt) f, chlorophyll (Chl) a, and Chl b in sugar beet leaves.
Abstract: It has been proposed that Fe stress may be used in the study of limiting factors in photosynthesis as an experimental means of varying photochemical capacity in vivo (Plant Physiol 1980 65: 114-120). In this paper the effect of Fe stress on photosynthetic unit number, size, and composition was investigated by measuring P(700), cytochrome (Cyt) f, chlorophyll (Chl) a, and Chl b in sugar beet leaves. The results show that when Fe stress reduced Chl per unit area by 80% (from 60 to 12 micrograms per square centimeter), it decreased the number of P(700) molecules per unit area by 88% and Cyt f per unit area by 86%; over the same range the Chl to P(700) ratio increased by 37% but there was no significant change in the Chl to Cyt f ratio. These data suggest that Fe stress decreases photochemical capacity and Chl per unit area by diminishing the number of photosynthetic units per unit leaf area.The ratio of Chl a to Chl b did not change with Fe stress. This suggests that the proportion of light-harvesting Chl a/b-protein complex within the photosynthetic unit remained constant. Electron microscopy of chloroplasts revealed that the decrease in the number of photosynthetic units which occurred during Fe stress was accompanied by a reduction in the number of granal and stromal lamellae per chloroplast and by a reduction in the number of thylakoids per granum.

Book
01 Jan 1980
TL;DR: The chemical nature of photosynthesis, the roles of chlorophylls and other pigments, and the role of two quanta or two photosystems in photosynthesis are discussed in this article.
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.

Book ChapterDOI
TL;DR: This chapter focuses on the phycobilisome characteristics, their relationship to the photosystems in the thylakoid membrane, and major problems to be addressed in future investigations.
Abstract: Publisher Summary Phycobilisomes are specialized aggregated structures composed of phycobiliproteins, which are photosynthetic accessory pigments in red and blue-green algae. Phycobiliproteins, which can account for as much as 24% of the dry weight of blue-green algal cells and 40–60% of the total soluble protein, are the major light harvesters in these organisms. Chlorophyll a, which absorbs light primarily in the blue region and the red region of the visible spectrum, leaves a large absorption gap. This is filled in by the phycobiliproteins, which have an absorption range of 500–660 nm. These pigments work in conjunction with chlorophyll a to optimize light harvesting for photosynthesis, particularly under light limiting conditions. The only phycobiliprotein in higher plants is phytochrome, which occurs in very small amounts and serves as a photoregulatory receptor. In cryptophyte algae (flagellated unicells of indefinite taxonomic position), phycobiliproteins also serve as major photosynthetic accessory pigments, but phycobilisomes are absent. There are three major classes of phycobiliproteins—the red-colored phycoerythrins (PEs), the blue-colored phycocyanins (PCs), and allophycocyanins (APCs). This chapter focuses on the phycobilisome characteristics, their relationship to the photosystems in the thylakoid membrane, and major problems to be addressed in future investigations.

Journal ArticleDOI
TL;DR: Remarkable constancy of these ratios, in spite of wide variation in cell material, supports an hypothesis that in A. nidulans there are two chlorophyll proteins, each bearing a reaction center and chlorophyLLs in fixed ratio.
Abstract: Spontaneous pigment mutants of Anacystis nidulans were self-selected for improved growth in far red light (> 650 nanometers). Questions were asked about those features of the light-harvesting mechanism which altered to give the mutants improved photosynthetic performance in far red. Answers were sought by comparing pigment and reaction center concentrations for the parent and six mutants grown in gold fluorescent and in far red light. Three significant results emerged. The ratio of reaction centers for photoreactions I and II (RC1/RC2) varied by a value of about 2.1 for all clones grown in gold and a value of about 1.1 for all clones grown in far red. Alteration of the ratio was not evident in any of the mutants.Phycobilisome alterations were evident as decreased phycocyanin content in all mutants. In three mutants, allophycocyanin became the major remaining phycobilisome component. Action spectra for photoreactions I and II allowed estimates of chlorophylls serving each of the two reaction centers. Ratios of chlorophylls to reaction centers within each photosystem were chlorophyll I/RC1 = 118 +/- 11 and chlorophyll II/RC2 = 52 +/- 9 for all seven clones grown in both gold and far red light. Remarkable constancy of these ratios, in spite of wide variation in cell material, supports an hypothesis that in A. nidulans there are two chlorophyll proteins, each bearing a reaction center and chlorophylls in fixed ratio.

Journal ArticleDOI
TL;DR: In this article, the formation of coccolithophorids was evaluated by two new methods: carbon fixation is measured at 10-s intervals in the first 2 min after addition of CO, and II''CO,- to buffered cultures; this method exploits the relatively long half-time for the hydration or dehydration of dissolved COP.
Abstract: The concept that the formation ofCnC0, coccoliths functions as a photosynthetic adaptation for the use of bicarbonate is evaluated in the coccolithophorids Coccoliths hudeyi and Cricosphneru carterae by two new methods. In the first, carbon fixation is measured at 10-s intervals in the first 2 min after addition of “CO, and II’“CO,- to buffered cultures; this method exploits the relatively long half-time for the hydration or dehydration of dissolved COP. In the second, shifts in pH and alkalinity resulting from carbon fixation by cells growing in liqllid culture are assessed to indicate fluxes of COz and HC03- into cells and these values compared to measurements of l”C incorporation in photosynthesis and carbonate deposition. The data are interpreted in terms of one of several net inorganic reactions of deposition considered. In this reaction, CO, is the substrate of photosynthesis and HCO,- is the form of carbon supplied to the calcification site. CO, resulting from carbonate deposition supplements the COz from the medium

Journal ArticleDOI
TL;DR: The fractionation of H isotopes between the water in the growth medium and the organically bonded H from microalgae cultured under conditions, where light intensity and wavelength, temperature, nutrient availability, and the H isotope ratio of the water were controlled, is reproducible and light dependant as discussed by the authors.

Journal ArticleDOI
TL;DR: Results demonstrate that the heat-induced damage to the photosynthetic apparatus involves not only a functional dissociation of the chlorophyll a/b light-harvesting complex from the photosystem Ii complex, but a physical dissociation as well.

Journal ArticleDOI
TL;DR: It is concluded that the causes of the induction lag in protoplasts can differ from those in isolated chloroplasts, and it is suggested that fructose-1,6-bisphosphatase and ribulose- 1,5-bisPhosphate carboxylase may limit flux in the Calvin cycle during induction.

Journal ArticleDOI
TL;DR: The higher growth rates of the diatoms were shown to be related to their higher photosynthetic rates per unit carbon, and the ecological significance of the physiological difference between these two groups of microalgae is discussed.
Abstract: Photosynthetic rates, growth rates, cell carbon, cell protein, and chlorophyll a content of two diatom and two dinoflagellate species were measured. The microalgae were chosen to have one small and one large species from each phylogenetic group; the two size categories differed from each other by 1.5 orders of magnitude in terms of cell carbon or cell protein. The cultures for the experiments were grown under continuous light at an irradiance high enough for the light-saturation of growth for all four species. The four species were found to have similar maximum photosynthetic rates per unit chlorophyll a. The diatom species showed lower carbon/chlorophyll a ratios and higher photosynthetic rates per unit carbon than the dinoflagellates. The higher growth rates of the diatoms were shown to be related to their higher photosynthetic rates per unit carbon. The ecological significance of the physiological difference between these two groups of microalgae is discussed.

Journal ArticleDOI
TL;DR: The pattern of carbon flow into the major end products of photosynthesis appeared to be the same for a given photosynthetic rate regardless of irradiance level, and colonies at the second station were interpreted to have been in a nutritionally poor state.
Abstract: Surface populations of Oscillatoria thiebautii (Corn.) Geitler in the Caribbean Sea are exposed to photoinhibiting irradiances throughout most of the 12-h light period. Oxygen inhibition of carbon assimilation at high irradiance suggested that photoinhibition was partly due to photorespiration. The pattern of carbon flow into the major end products of photosynthesis appeared to be the same for a given photosynthetic rate regardless of irradiance level. At one station, enhanced relative rates of protein synthesis were observed at low rates of photosynthesis. At another station, this effect was not observed but the proportion of 14C in polysaccharide was low while that in metabolites was high. On the basis of previous findings, colonies at the second station were interpreted to have been in a nutritionally poor state. The rates at which intracellular macromolecular pools approached saturation seemed to depend on the rate of photosynthesis.

Journal ArticleDOI
TL;DR: Three mutants of the crucifer Arabidopsis thaliana (Linnaeus) Heynhold were isolated that are completely lacking in activity catalyzed by serine-glyoxylate aminotransferase, which may permit the direct selection of secondary mutations that reduce photorespiration.
Abstract: Three mutants of the crucifer Arabidopsis thaliana (Linnaeus) Heynhold were isolated that are completely lacking in activity catalyzed by serine-glyoxylate aminotransferase (EC 2.6.1.45), a peroxisomal enzyme involved in photorespiratory carbon metabolism. These mutants were viable and exhibited normal photosynthesis under conditions that suppressed photorespiration, but they were inviable and photosynthesized at greatly reduced rates under conditions that promoted photorespiration. Serine and glycine accumulated as end products of photosynthesis in the mutants, mostly at the expense of starch and sucrose. The mutants are allelic, and the segregation patterns of plant viability, photosynthetic activity, and enzyme activity in the F1 and F2 generations indicated that all the observed effects were caused by a single recessive nuclear mutation. This conclusion was confirmed by the isolation of seven revertants in which viability, photosynthetic capacity, and enzyme activity were simultaneously restored. Mutants of the type described here, in which photorespiration is changed from a merely wasteful process into one that is lethal, may permit the direct selection of secondary mutations that reduce photorespiration.

Journal ArticleDOI
TL;DR: It is suggested that Zn inhibits electron flow at the oxidizing side of photosystem II at a site prior to the electron donating site(s) of hydroxylamine and diphenylcarbazide, and with concentrations of ZnSO(4) above 5 millimolar, photosystem I activity is partially inactivated.
Abstract: In isolated barley chloroplasts, the presence of 2 millimolar ZnSO4 inhibits the electron transport activity of photosystem II, as measured by photoreduction of dichlorophenolindophenol, O2 evolution, and chlorophyll a fluorescence. The inhibition of photosystem II activity can be restored by the addition of the electron donor hydroxylamine or diphenylcarbazide, but not by benzidine and MnCl2. These observations suggest that Zn inhibits electron flow at the oxidizing side of photosystem II at a site prior to the electron donating site(s) of hydroxylamine and diphenylcarbazide. No inhibition of photosystem I-dependent electron transport by 3 millimolar ZnSO4 is observed. However, with concentrations of ZnSO4 above 5 millimolar, photosystem I activity is partially inactivated. Washing Zn2+-treated chloroplasts partially restores the O2-evolving activity.


Journal ArticleDOI
TL;DR: Hydrilla does not fit any of the present photosynthetic categories, and may have to be placed into a new group, together with other submersed aquatic macrophytes that have environmentally variable CO(2) compensation points.
Abstract: The CO 2 compensation point of the submersed aquatic macrophyte Hydrilla verticillata varied from high (above 50 microliters per liter) to low (10 to 25 microliters per liter) values, depending on the growth conditions Plants from the lake in winter or after incubation in an 11 C/9-hour photoperiod had high values, whereas summer plants or those incubated in a 27 C/14-hour photoperiod had low values The plants with low CO 2 compensation points exhibited dark 14 CO 2 fixation rates that were up to 30% of the light fixation rates This fixation reduced respiratory CO 2 loss, but did not result in a net uptake of CO 2 at night The low compensation point plants also showed diurnal fluctuations in titratable acid, such as occur in Crassulacean acid metabolism plants However, dark fixation and diurnal acid fluctuations were negligible in Hydrilla plants with high CO 2 compensation points Exposure of the low compensation point plants to 20 micromolar 14 CO 2 resulted in 60% of the 14 C being incorporated into malate and aspartate, with only 16% in sugar phosphates At a high CO 2 level, the C 4 acid label was decreased A pulse-chase study indicated that the 14 C in malate, but not aspartate, decreased after a long (270-second) chase period; thus, the C 4 acid turnover was much slower than in C 4 plants Phosphoenolpyruvate carboxylase activity was high (330 micromoles per milligram chlorophyll per hour), as compared to ribulose bisphosphate carboxylase (20 to 25), in the plants with low compensation points These plants also had a pyruvate, Pi dikinase activity in the leaves of 41 micromoles per milligram chlorophyll per hour, which suggests they are not C 3 plants NAD- and NADP + -malate dehydrogenase activities were 6136 and 245 micromoles per milligram chlorophyll per hour, respectively Of the three decarboxylating enzymes assayed, the activities of NAD- and NADP + -malic enzyme were 1042 and 237 micromoles per milligram chlorophyll per hour, while phosphoenolpyruvate carboxykinase was only 02 Low compensation point Hydrilla plants fix some CO 2 into C 4 acids, which can be decarboxylated for later refixation, presumably into the Calvin cycle Refixation would be advantageous in summer lake environments where the CO 2 levels are high at night but low during the day Hydrilla does not fit any of the present photosynthetic categories, and may have to be placed into a new group, together with other submersed aquatic macrophytes that have environmentally variable CO 2 compensation points


Journal ArticleDOI
TL;DR: The response of apparent photosynthesis to N nutrition was studied in the C(3) grass, tall fescue, and in Panicum milioides Nees ex Trin.
Abstract: The response of apparent photosynthesis to N nutrition was studied in the C 3 grass, tall fescue ( Festuca arundinacea Schreb.), in the C 4 species Panicum maximum Jacq., and in Panicum milioides Nees ex Trin., a species with characteristics intermediate between C 3 and C 4 photosynthetic types. Plants were grown in culture solution containing 1, 5, 50, and 200 milligrams N per liter. Apparent photosynthesis was measured on the youngest fully expanded leaves at 320 microliters of CO 2 per liter of air and 21% O 2 . Leaf conductance was calculated from transpiration measurements, and CO 2 compensation concentrations were also estimated. Several leaf anatomical characteristics were studied on plastic-embedded material. Leaf N content was determined on leaves which were used in photosynthesis measurements. Apparent photosynthesis increased in a linear fashion with increases in leaf N content in all three species. The increase in apparent photosynthesis per unit increase in leaf N was over twice as great in P. maximum (9.7 milligrams CO 2 per square decimeter per hour for each increase of 1% leaf N) as in P. milioides and tall fescue. Apparent photosynthesis and its response to N level were similar in P. milioides and tall fescue, but at leaf N concentrations above 2%, apparent photosynthesis in these two species was only about one-half of that in P. maximum. Increases in apparent photosynthesis due to higher N levels were accompanied by increases in both leaf and mesophyll conductances in P. maximum, whereas in P. milioides and tall fescue only mesophyll conductance was significantly correlated with leaf N. Water use efficiency (apparent photosynthesis/transpiration) increased in a linear manner with increased leaf N in all three species but was more closely related to leaf N in P. milioides and tall fescue than in P. maximum. High N levels tended to increase leaf thickness and interveinal distance in all three species. The percentage of air space in leaf tissue and the mesophyll cell diameter were either not affected or changed only slightly by N nutrition with the exception that percentage of air space in tall fescue leaves rose from 17.3 to 24.8 with an increase in solution N level from 1 to 200 milligrams per liter. Although P. milioides has been shown to have photosynthetic and leaf anatomical characteristics intermediate to C 3 and C 4 species, its response to N was similar to that of the C 3 grass, tall fescue.

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TL;DR: Phytoplankton can bring about photo-induced changes in photosynthesis very quickly and thus accommodate widely fluctuating light regimes over short periods of time, and compared well with time-course phenomena reported for other groups of phytopLankton.
Abstract: Cultures of the marine dinoflagellate Glenodinium sp. were light-shifted and rates of photoadaptation determined by monitoring changes in cell volume, growth rate, pigmentation, parameters of the photosynthesisirradiance (P-I) curves and respiration. To approximate physiological conditions of field populations, cells were cultured on an alternating light-dark cycle of 12hL:12hD, which introduced a daily periodicity of photosynthesis. One result of the present study was to demonstrate how specific parameters of the P-I relationship influenced by periodicity of the light: dark cycle are distinguished from photosynthetic parameters influenced by changes in light level. Under steady-state conditions, rates of both light-saturated (Pmax) and light-limited photosynthesis changed in unison over the day; these changes were not related to pigmentation, and displayed their maxima midday. This close relationship between Pmax and the slope (a) of the cellular P-I curves in steadystate conditions was quickly adjusted when growth illumination was altered. Rates of light-limited photosynthesis were increased under low light conditions and the periodicity of cellular photosynthesis was maintained. The short-term responses of the P-I relationship to changing light level was different, depending on (1) whether the light shift was from high to low light or vice versa, and (2) whether the high light levels were sufficient to promote maximal photosynthesis rates. Major increases in the photosynthetic carotenoid peridinin, associated with a single type of light-harvesting chromo protein in the chloroplast, was observed immediately upon shifting high light cultures to low light conditions. Following pigment synthesis, significant increases in rates of light-limited photosynthesis were observed in about one-tenth the generation time, while cellular photosynthetic potential was unaffected. it is suggested that general results were consistent with suggested that general results were consistent with earlier reports that the major photoadaptive “strategy” of Glenodinium sp. is to alter photosynthetic unit (PSU) size. Photoadaptive response times to high light were light-dependent, but appeared to be shower than photoadaptive responses to low light. If light intensities were bright enough to maximize growth rates, photosynthetic response times were on the order of a generation period and pigmentation fell quickly as cells divided at a faster rate. If light-intensities were not sufficient to maximize growth rates, then pigment content did not decline, while rates of light-limited photosynthesis declined quickly. In all cases, photoadaptation was followed best by monitoring fast changes in half saturation constants for photosynthesis, rather than fluctuating changes in pigmentation. Results compared well with time-course phenomena reported for other groups of phytoplankton. Overall, results suggest phytoplankton can bring about photo-induced changes in photosynthesis very quickly and thus accommodate widely fluctuating light regimes over short periods of time.

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TL;DR: The delta(13)C values for seagrasses collected along the Texas Gulf Coast range from -10.9 to -11.4 per thousand, which are similar to the delta( 13)C value of terrestrial C(4) plants, but seagRasses lack bundle sheath cells which are important in determining the delta-13C values of C( 4) plants.
Abstract: The δ 13 C values for seagrasses collected along the Texas Gulf Coast range from −10.9 to −11.4‰. These values are similar to the δ 13 C values of terrestrial C 4 plants, but seagrasses lack bundle sheath cells which are important in determining the δ 13 C values of C 4 plants. This work attempts to explain the reason the δ 13 C values of seagrasses resemble the δ 13 C values of C 4 plants. Investigations on the photosynthetic characteristics of seagrasses show that dissolved CO 2 is the species of inorganic carbon absorbed or accumulated by Thalassia testudinum. The rate of photosynthetic CO 2 fixation varies from 9.6 to 129.0 micromoles CO 2 per milligram chlorophyll per hour in the presence of 0.042 to 1.9 millimolar dissolved CO 2 due to the high resistances of Thalassia leaves to CO 2 diffusion. Phosphoglyceric acid is the first stable product of photosynthetic CO 2 fixation in Thalassia which is a Calvin cycle plant. The light/dark ratios of 14 CO 2 release from submerged Thalassia leaf sections at 1, 21, and 100% O 2 indicate a small apparent photorespiration. Dark respiration continues in the light and is stimulated by 21 and 100% O 2 . The low apparent photorespiration may be due to membrane and H 2 O resistances to CO 2 diffusion with subsequent refixation of the photorespired CO 2 . The internal pool of CO 2 is not in equilibrium with the external pool of CO 2 which results in a closed system in the seagrasses. The δ 13 C value of CO 2 in sea H 2 O in isotopic equilibrium with HCO 3 − is −10.3‰ and the δ 13 C value of hexoses isolated from the leaves of Thalassia is −11.5‰. In the closed system of the seagrasses there is a −1.2‰ fractionation of CO 2 by ribulose-1,5-bisphosphate carboxylase and the Calvin cycle. This contrasts to a fractionation of about −17 to −27‰ of the stable carbon isotopes of CO 2 by the Calvin cycle in the open system of terrestrial C 3 plants where the internal pool of CO 2 is in equilibrium with atmospheric CO 2 . Among C 3 plants the seagrasses are very unusual in fixing CO 2 by the Calvin cycle in a closed system. This closed system metabolism is analogous to the fixation of CO 2 by the Calvin cycle in the bundle sheath cells of C 4 plants where all of the 12 CO 2 and 13 CO 2 is fixed by ribulose-1,5-bisphosphate carboxylase. Therefore, the reasons the δ 13 C values of seagrasses and C 4 plants are similar are: ( a ) the δ 13 C value of dissolved CO 2 in seawater resembles the δ 13 C value of the C 4 acids and the δ 13 C value of CO 2 in the bundle sheath cells, and ( b ) there is no fractionation of the stable carbon isotopes of CO 2 in the closed systems of the seagrasses or the bundle sheath cells of C 4 plants.

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TL;DR: The main finding from the budget was that carbon production and its utilization by bolls is out of phase both at the node and whole plant level which necessitates considerable movement of carbon among nodes and into and out of storage.
Abstract: A carbon budget for cotton plants at the single leaf, node and whole plant level was constructed using data from four glasshouse experiments. Data were collected on leaf expansion and dry weight growth, net photosynthesis, dark respiration of leaves and stems and on responses of photosynthesis to light in tissues of different age. The potential export of carbon by leaves was calculated as daily net photosynthesis less requirements for growth and dark respiration. The carbon budget for the single leaf showed that the leaf's maximum requirement occurred 7-8 days after unfolding, at the same time as it became a net carbon exporter. Dark respiration used most carbon at days 12-15 but even then the amount was only about 10% of the carbon fixation by the leaf during the day. Potential carbon export reached a peak in 22-day-old leaves, approximating 1 mg C cm-2 day -1 on a sunny day. The main finding from the budget was that carbon production and its utilization by bolls is out of phase both at the node and whole plant level which necessitates considerable movement of carbon among nodes and into and out of storage. This finding was confirmed in a study using 14CO2 which, while supporting the general hypothesis that the plant's carbon is fed into a pool available to all organs, indicated that there are preferred links between node positions in vertical alignment.

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TL;DR: In this paper, photosynthetic rates of coffee plants grown under the full sun and shade were compared and it was concluded that coffee is more suited to high density plantings where mutual shading, resulting in low light intensities and lower leaf temperatures, are likely to produce a favourable environment for efficient photosynthesis and growth.
Abstract: Photosynthetic rates of coffee plants grown under the full sun and shade were compared. The saturating irradiance of 300 μE−1 m s−1 of shade plants shifted to near 600 μE in sungrown plants, but shade plants possessed substantially higher photosynthetic rates. Photosynthetic rates decreased above 25°C, which was apparently due to a decline in the mesophyll conductance, as stomatal conductance remained more or less unchanged between 25° and 35°C. Most of these measurements were made on seedlings in plastic bags. It is concluded that coffee is more suited to high density plantings where mutual shading, resulting in low light intensities and lower leaf temperatures, are likely to produce a favourable environment for efficient photosynthesis and growth.