Showing papers on "Photosynthesis published in 1970"
TL;DR: Calculated productivity of various calcareous algal zones indicates that these do not contribute significantly to overall reef production on atolls of the northern Marshall Islands, and island reefs are less productive than previously studied inter—island reefs.
Abstract: Primary productivity of reef—building algae was studied by putting samples from the reef in a closed system and measuring oxygen exchange in the light and in the dark Gross productivity determined for 32 samples in full sunlight had a mean value of 0048 mg O2 cm—2 hr—1 Photosynthesis was found to increase with the logarithm of light intensity up to 1,000 ft—c and was constant between 1,000 and 8,000 ft—c Rates of gas exchange in flowing water showed no correlation with water velocity but were greater than rates in still water Daily patterns of photosynthesis were calculated for populations of calcareous algae living on the submarine faces of the windward sides of atolls During most of the daylight hours light is probably not a limiting factor for photosynthesis in these populations Calculated productivity of various calcareous algal zones indicates that these do not contribute significantly to overall reef production on atolls of the northern Marshall Islands Island reefs are less productive than previously studied inter—island reefs
503 citations
TL;DR: In this article, the authors propose a method to solve the problem of the problem: this article...,.. ].. ).. ]... )...
Abstract: CONTENTS
328 citations
TL;DR: The activity of these enzymes in different species with the C(4)-dicarboxylic acid pathway was compared and their possible role in photosynthesis was considered.
Abstract: 1. NADP-malate dehydrogenase and ;malic' enzyme in maize leaf extracts were separated from NAD-malate dehydrogenase and their properties were examined. 2. The NADP-malate dehydrogenase was nicotinamide nucleotide-specific but otherwise catalysed a reaction comparable with that with the NAD-specific enzyme. By contrast with the latter enzyme, a thiol was absolutely essential for maintaining the activity of the NADP-malate dehydrogenase, and the initial velocity in the direction of malate formation, relative to the reverse direction, was faster. 3. For the ;malic' enzyme reaction the K(m) for malate was dependent on pH and the pH optimum varied with the malate concentration. At their respective optimum concentrations the maximum velocity for this enzyme was higher with Mg(2+) than with Mn(2+). 4. The NADP-malate dehydrogenase in green leaves was rapidly inactivated in the dark and was reactivated when plants were illuminated. Reactivation of the enzyme extracted from darkened leaves was achieved simply by adding a thiol compound. 5. The activity of both enzymes was low in etiolated leaves of maize plants grown in the dark but increased 10-20-fold, together with chlorophyll, when leaves were illuminated. 6. The activity of these enzymes in different species with the C(4)-dicarboxylic acid pathway was compared and their possible role in photosynthesis was considered.
251 citations
TL;DR: It was concluded that the C(4) pathway confers no particular ability to withstand low leaf water potentials and corn was less able to withstand severe desiccation without tissue death.
Abstract: Rates of net photosynthesis were studied in soil-grown corn (Zea mays) and soybean (Glycine max) plants having various leaf water potentials. Soybean was unaffected by desiccation until leaf water potentials were below -11 bars. Rates of photosynthesis in corn were inhibited whenever leaf water potentials dropped below -3.5 bars.The differences in photosynthetic behavior could be attributed solely to differences in stomatal behavior down to leaf water potentials of -16 bars in soybean and -10 bars in corn. Below these potentials, other factors in addition to stomatal closure caused inhibition, although their effect was relatively small.Corn, which has the C(4)-dicarboxylic acid pathway for carbon fixation, generally had a higher rate of photosynthesis than soybean during desiccation. Nevertheless, since inhibition of photosynthesis began at higher potentials than in soybean, and since corn was less able to withstand severe desiccation without tissue death, it was concluded that the C(4) pathway confers no particular ability to withstand low leaf water potentials.
243 citations
TL;DR: It is concluded that the inhibition of electron transport by the quinone occurs between photosystem I and II and close to or at the functional site of plastoquinone.
Abstract: A halogenated benzoquinone has been found to inhibit the photosynthetic electron transport system in isolated chloroplasts 2·10⁻⁶ᴍ of dibromo-thymoquinone inhibit the Hill- reaction with NADP, methylviologen or anthraquinone to 100%, but do not effect the photoreduction of NADP at the expense of an artificial electron donor The Hill - reaction with ferricyanide is inhibited even at the high concentration of 2·10⁻⁵ᴍ of dibromo-thymoquinone to only 60% The remaining reduction in the presence of the inhibitor reflects the rate of ferricyanide reduction by photosystem II It is concluded that the inhibition of electron transport by the quinone occurs between photosystem I and II and close to or at the functional site of plastoquinone
219 citations
TL;DR: It was concluded that moderately low leaf water potential affects photosynthesis in at least two ways: first, through an inhibition of oxygen evolution by chloroplasts and, second, by closure of stomata in intact leaves.
Abstract: Chloroplasts were isolated from pea and sunflower leaves having various water potentials. Oxygen evolution by the chloroplasts was measured under identical conditions for all treatments with saturating light and with dichloroindophenol as oxidant. Evolution was inhibited when leaf water potentials were below -12 bars in pea and -8 bars in sunflower and the inhibition was proportional to leaf water potential below these limits. Inhibition was more severe in sunflower than in pea chloroplasts. In sunflower, it could be detected after 5 minutes of leaf desiccation, and, up to 1 hour, the effect was independent of the duration of low leaf water potential.In high light, the reduction in activity of sunflower chloroplasts paralleled the reduction in CO(2) fixation by intact sunflower plants having low leaf water potentials. Stomatal apertures and transpiration rates were also reduced under these conditions and were probably limiting. In low light, intact sunflowers required more light per unit of CO(2) fixed when leaf water potentials were low than when they were high. This increased light requirement in the intact system was of a magnitude which could be predicted from the reduced oxygen evolution by the isolated chloroplasts. It was concluded that moderately low leaf water potential affects photosynthesis in at least two ways: first, through an inhibition of oxygen evolution by chloroplasts and, second, by closure of stomata in intact leaves.
142 citations
TL;DR: In this paper, the rates of photosynthesis (carbon dioxide fixation in the light expressed on a per unit chlorophyll or per unit fresh-weight basis) and respiration (Carbon dioxide evolution in the dark expressed on either per unit nitrogen, phosphorus, sulphur, manganese, zinc and molybdenum deficiencies resulted in reduced respiration rates.
Abstract: Spinach plants were grown in nutrient-culture solutions containing reduced levels of all the macro- and micro-nutrient elements except cobalt and chlorine. The rates of photosynthesis (carbon dioxide fixation in the light expressed on a per unit chlorophyll or per unit fresh-weight basis) and respiration (carbon dioxide evolution in the dark expressed on a per unit nitrogen or per unit fresh-weight basis) for whole plants were measured using infra-red gas analysis techniques. Measurements were made when the plants displayed clear symptoms of deficiency relative to control plants. All nutrient deficiencies except iron and molybdenum depressed photosynthesis when chlorophyll was the basis of calculation; manganese-, copper-, phosphorus- and potassium-deficient plants showed the greatest depression. Alternatively when photosynthesis was calculated on a fresh weight basis calcium was the only deficiency which had no affect. Similarly when respiration was calculated on a nitrogen basis all deficiencies except iron, molybdenum and nitrogen result in depressed rates but when respiration was expressed on a fresh-weight basis potassium deficiency resulted in enhanced respiration rates and nitrogen, phosphorus, sulphur, manganese, zinc and molybdenum deficiencies resulted in reduced respiration rates.
141 citations
TL;DR: In this paper, the nitrogen oxides (NO2 and NO) inhibited apparent photosynthesis of oats and alfalfa at concentrations below those required to cause visible injury, and there appeared to be a threshold concentration of about 0.6 ppm for each pollutant.
131 citations
TL;DR: The photosynthesis-light curve for purple sulfur bacteria had a steeper inclination than that for green sulfur bacteria at low light intensities, and the properties of the growth phase observed in lakes were similar to those calculated.
Abstract: The photosynthesis-light curve for purple sulfur bacteria had a steeper inclination than that for green sulfur bacteria at low light intensities. Light saturation occurred at intensities of S-7 klux in the former, in the latter at 10-30 klux. Light inhibition was observed in purple sulfur bacteria but was negligible in green sulfur bacteria. The optimal temperature for photosynthesis of these bacteria is considerably higher than that of most phytoplankton or green plants. Photosynthetic sulfur bacteria appear ordinarily in the contact layer between oxidative and reductive zones of meromictic or stagnant holomictic lakes; the light intensity in this contact layer is usually less than 10% of that at the surface. On the assmuption that the photosynthetic rate of these bacteria is limited mainly by the interaction of hydrogen sulfide concentration with light intensity, their growth was analyzed with a mathematical model. The properties of the growth phase observed in lakes were similar to those calculated. The main factors determining the growth of photosynthetic sulfur bacteria in lakes are the II23 concentration in the upper layer and the light conditions in the deeper layer.
131 citations
TL;DR: In this article, the authors present a series-based approach to the analysis of photosynthesis in plants and algae, where each pigment is complexed to its own chain of electron carriers, the complexes being termed photosystem I (PS-I) and photosystem II(PS-II).
Abstract: I t is now well established that photosynthesis in plants and algae involves two photochemical reactions catalyzed by light absorbed by two different pigment assemblies (see 14, 48, 72 for recent reviews). Each pigment as sembly is complexed to its own chain of electron carriers, the complexes being termed photosystem I (PS-I) and photosystem II (PS-II) . The formulation of photosynthesis which is currently accepted by the majority of research workers in the area is a series one, in which the photosystems cooperate in a sequential manner. Reduction of NADP+ is catalyzed by PS-l , while PS-II is involved in the oxidation of water. Arnon et al. (6, 7, 75) have proposed an alternative hypothesis (a parallel formulation) in which PS-I is limited to cyclic photophosphorylation, whereas PS-II is involved in noncyclic electron flow from water to NADP+ and noncyc1ic phosphorylation. At the present time the weight of experimental evidence favors the series formulation (14, 48, 72). The parallel formulation also seems improbable on thermodynamic grounds (37, 95). The light phase of photosynthesis is performed on the internal membranes (thylakoids) of the chloroplast. This means that either PS-I and PS-II are an integral part of the membranes or they are structures which are intimately associated with the membranes. One approach to an understanding of the molecular organization of the photochemical systems is to selectively frag ment the membranes so as to release specific components or complexes of the photosynthetic electron transport chain, and to study the properties of the isolated complexes. The number of studies along these lines have increased rapidly over the past 5 years, and they form the subject of this review.
117 citations
TL;DR: It is concluded that plastocyanin is likely to be the only copper compound involved in photosynthetic electron transport.
TL;DR: Using manometric techniques, H(2) evolution in both darkness and light has been studied in the green alga, Chlamydomonas moewusii, and results indicate that oxidative carbon metabolism is the source of reductant for the reaction.
Abstract: Using manometric techniques, H(2) evolution in both darkness and light has been studied in the green alga, Chlamydomonas moewusii.Hydrogen evolution in the dark is accompanied by the release of only CO(2) in manometrically detectable amounts. It is depressed by dark starvation and inhibited both by monofluoroacetic acid and by uncouplers of phosphorylation. This evidence suggests that the reaction is dependent on oxidative carbon metabolism for reductant and phosphorylation for energy to raise the reductant to a redox potential capable of reducing H(+).Photoevolution of H(2) is also accompanied by the release of only CO(2). It is depressed by dark starvation and stimulated by acetate or a period of photosynthesis. Monofluoroacetic acid causes complete inhibition, while 3-(3,4-dichlorophenyl)-1,1-dimethylurea causes no or only slight inhibition. These results indicate that oxidative carbon metabolism is the source of reductant for the reaction. Photoevolution of H(2) does not show Emerson enhancement, and it has an action spectrum peaking at a longer wave length than that of photosynthesis. These characteristics, together with the slight effect of 3-(3,4-dichlorophenyl)-1,1-dimethylurea on the reaction, show that only system I of photosynthetic electron transport is involved in the reaction. Photoevolution of H(2) is stimulated by uncouplers; this indicates that the role of light is not to provide energy by phosphorylation. Rather, the results support an electron flow driven directly by light through system I from reductant produced in oxidative carbon metabolism to a redox potential capable of reducing H(+).
TL;DR: The results indicate the division of the members of several genera into two groups, and leaf anatomy, gas exchange, 14CO2 labeling, and carbon isotope ratio showed exact correlations in the species tested.
Abstract: Several methods are described for measuring some aspect of the photosynthetic apparatus. The results indicate the division of the members of several genera into two groups. Leaf anatomy, gas exchange, 14CO2 labeling, and carbon isotope ratio showed exact correlations in the species tested. The strengths and weaknesses of some of the techniques are indicated.
TL;DR: In this article, the change in the potential photosynthetic capacity and the behavior of the photo-ynthetic quotient were investigated during the life cycle of Scenedesmus obliquus under a light-dark regime of 14:10 hours.
Abstract: Using synchronous cultures, the change in the potential photosynthetic capacity and the behavior of the photosynthetic quotient were investigated during the life cycle of Scenedesmus obliquus, strain D 3.
Scenedesmus obliquus was synchronized under a light-dark regime of 14:10 hours. The quality of synchrony was demonstrated by complete synchronization, homogeneity, exponential growth, shortest possible life cycle and non-susceptibility of the life cycle to the synchronizing procedure. Furthermore, the synchronous culture was characterized by determination of cell number, dry weight, packed cell volume, chlorophylls a and b and the carotenoids during the life cycle. The potential photosynthetic capacity (as O2 evolution) was measured manometrically and polarographically in white light. This capacity increased from the beginning of the light period until the 8th hour and then declined until the 16th hour, that is until just before release of daughter cell. The percentage difference between the maximum and the minimum of the photosynthetic capacity was the same in the light saturating and light limiting region of photosynthesis. — The photosynthetic quotient was measured by means of Warburg's “indirect method”. It proved to be constant throughout the life cycle under light saturating and light limiting conditions. The ratio of O2 evolved to CO2 consumed was just below unity. The results were compared with those of other authors and their significance was discussed. It was concluded that the change in the photosynthetic capacity is inherent in the normal life cycle of green algae and is not a result of the synchronizing light-dark regime.
TL;DR: Spinach chloroplast carbonic anhydrase is found to be inhibited by diamox, nitrate, nitrite, and halide ions, which is consistent with the view that both the formation of CO 2 from bicarbonate ions at thechloroplast surface and a further reaction ofCO 2 or bICarbonate within the chloroplasts must be catalysed by carbonicAnhydrase in order to obtain maximum rates of photosynthesis.
TL;DR: An oxygen-insensitive postillumination CO2 burst occurs in many plants with the C4-pathway of photosynthesis and is absent in C 4-species that produce mainly malate in short-term photosynthesis, while some malate formers show extreme grana reduction in bundle sheath chloroplasts which, is associated with a low capacity for generating reducing power.
Abstract: An oxygen-insensitive postillumination CO2 burst occurs in many plants with the C4-pathway of photosynthesis. C4-species with a postillumination burst synthesize mainly aspartate during very short ...
TL;DR: Ribulose 5-P kinase is activated up to 4 fold by intact photosynthesizing spinach chloroplast or by dark incubation of broken chloroplasts with dithiothreitol, blocked by O 2, arsenite, iodoacetamide and by dichlorophenyldimethylurea.
TL;DR: A more extensive survey of the fatty acid composition of blue–green algae, with particular attention to unicellular representatives, is undertaken.
Abstract: AMONG eukaryotes, α-linolenic acid (18 : 3α) and certain related polyunsaturated fatty acids occur as major fatty acids only in photosynthetic organisms1, where they are concentrated in chloroplasts as components of the acyl lipids2. Photosynthetic bacteria, by contrast contain saturated and monounsaturated fatty acids exclusively, a character which they share with nearly all non-photosynthetic bacteria3–5. Blue–green algae are the only prokaryotes which photosynthesize as do green plants, and their fatty acid composition is thus of particular interest from the evolutionary standpoint. Many filamentous blueαgreen algae have been shown to contain polyunsaturated fatty acids6,8,9, but these compounds are absent from three unicellular blue–green algae so far examined: Anacystis nidulans, Anacystis marina and Synechococcus cedrorum6,7,9. This has prompted us to undertake a more extensive survey of the fatty acid composition of blue–green algae, with particular attention to unicellular representatives.
TL;DR: The inhibition or slowing of starch translocation out of chloroplasts appears to account for reduced photo-synthesis and growth at low night temperatures.
Abstract: Growth of Digitaria decumbens is severely reduced by night temperatures of 10 degrees C or below. Ultra-structure of leaves and chemical analyses show a high starch content in chloroplasts of plants illuminated and kept at a temperature of 30 degrees C. This starch disappears after a period in the dark at 30 degrees C, but it remains if the temperature during the dark period is 10 degrees C. The inhibition or slowing of starch translocation out of chloroplasts appears to account for reduced photo-synthesis and growth at low night temperatures.
TL;DR: When 8-day seedlings were exposed to 14CO2 in light, approximately 2 hours were required for 14C to reach the apices of the roots and 14C exuded from intact roots into surrounding solutions was present in both volatile and non-volatile compounds.
Abstract: SUMMARY
When 8-day seedlings were exposed to 14CO2 in light, approximately 2 hours were required for 14C to reach the apices of the roots. One method used to detect the progress of 14C down the root was to scan the root with a radiochromatogram strip scanner. At this stage most 14C in aqueous ethanol extracts of roots was present as sucrose, equally labelled in glucose and fructose. This was converted only slowly to other components of the soluble fraction so that after 12 hours almost 50% of 14C was still retained in sucrose.
14C exuded from intact roots into surrounding solutions was present in both volatile and non-volatile compounds. In the non-volatile fraction glutamine, glutamic and aspartic acids were the main 14C-amino acids. Exudation of 14C was not affected by changing the inorganic composition of the collecting solution. A change in pH of collecting solution from 6.4 to 5.9 increased exudation. Exudation also increased markedly when 2,4-dinitrophenol or potassium cyanide was present in the collecting solution.
Journal Article•
TL;DR: The action spectrum of C 2 H 2 reduction indicates a primary involvement of Photosystem I in N 2 fixation by blue-green algae.
TL;DR: The light-induced increases in activity of enzymes of both the C4-dicarboxylic acid pathway and the Calvin cycle were inhibited by chloramphenicol, consistent with the hypothesis that the increases reflected synthesis of new enzyme on the 70S chloroplast ribosomes.
TL;DR: No deficiency other than low phosphoribulokinase activity was found which would account for the inability of cells of the mutant strain to fix carbon dioxide by photosynthesis, and the normal rates of nicotinamide adenine dinucleotide phosphate photoreduction and of photosynthetic phosphorylation observed in chloroplast fragments prepared from cells ofThe mutant strain indicated that the photosynthesis electron transport chain in the mutant is intact.
Abstract: A mutant strain of the unicellular green alga, Chlamydomonas reinhardi, is unable to fix carbon dioxide by photosynthesis because it is deficient in phosphoribulokinase activity. The absence of light-dependent carbon dioxide fixation in cells of the mutant strain supports the operation of the Calvin-Benson scheme of photosynthetic carbon dioxide fixation in this organism. No deficiency other than low phosphoribulokinase activity was found which would account for the inability of cells of the mutant strain to fix carbon dioxide by photosynthesis. Activities comparable to those in the wild-type strain were found for eight other enzymes of the Calvin cycle and two enzymes associated with the C(4) dicarboxylic acid pathway. The normal rates of nicotinamide adenine dinucleotide phosphate photoreduction and of photosynthetic phosphorylation observed in chloroplast fragments prepared from cells of the mutant strain indicated that the photosynthetic electron transport chain in the mutant is intact.
TL;DR: It seems likely that these results are indicative of a more active Photosystem I or a different size photosynthetic unit in C(4) cycle plants than in the reductve pentose phosphate cycle plants.
Abstract: Representative plants containing either the reductive pentose phosphate cycle or the C(4) dicarboxylic acid cycle of photosynthetic carbon dioxide fixation have distinctly different contents of P(700) and chlorophylls a and b. With leaf extracts and isolated chloroplasts from C(4) cycle plants, the mean value of the relative ratio of P(700) to total chlorophyll was 1.83 and the mean value of the ratio of chlorophyll a to b was 3.89. The respective values in similar extracts and chloroplasts from pentose cycle plants are 1.2 and 2.78.It seems likely that these results are indicative of a more active Photosystem I or a different size photosynthetic unit in C(4) cycle plants than in the reductve pentose phosphate cycle plants.
TL;DR: In both species, efficiency of water use decreased as temperature increased at all light intensities, and rates of photosynthesis were higher in sorghum than in wheat, with the greatest difference at high light levels.
Abstract: Wheat stomata offered less resistance to water and carbon dioxide diffusion than sorghum stomata at light intensities of 0·06 and 0·26 cal cm-2 min-i (400-700 nm) but resistances were comparable at 0·46 cal cm-2 min-i. Consequently, transpiration rates were higher in wheat than in sorghum, except at the high light levels, in leaf chamber experiments described here. Rates of photosynthesis were higher in sorghum than in wheat, with the greatest difference at high light levels. This resulted in a greater efficiency of dry matter production relative to water use in sorghum. Transpiration rate increased with increased temperature in both species. Photosynthesis was independent of temperature in wheat, and in sorghum under low light conditions, but otherwise photosynthesis increased with temperature in sorghum. In both species, efficiency of water use decreased as temperature increased at all light intensities. Water vapour concentration difference between the intercellular spaces and the air was comparable in wheat and sorghum and increased with temperature. The carbon dioxide concentration difference between air and intercellular spaces was substantially greater in sorghum than in wheat and increased with leaf temperature. Maximum values were obtained at the intermediate light level in sorghum.
TL;DR: When dark-grown cultures of Euglena were grown photoheterotrophically in light sufficient for the greening of the cells, or photosynthesis, manganese deficiency resulted in a reduction of the cellular content of chlorophyll and galactosyldiglycerides to 40% of control values, indicating interference with chloroplast formation.
Abstract: The growth of photoautotrophic Euglena gracilis Z is strongly inhibited by manganese deficiency, whereas chlorophyll formation is not appreciably affected. The galactosyldiglyceride content of the manganese-deficient photo-autotrophic Euglena was about 40% lower on the basis of either chlorophyll content or dry weight. When dark-grown cultures of Euglena were grown photoheterotrophically in light sufficient for the greening of the cells, or photosynthesis, manganese deficiency resulted in a reduction of the cellular content of chlorophyll and galactosyldiglycerides to 40% of control values, indicating interference with chloroplast formation. The fatty acids of the photoheterotrophic manganese-deficient cells were mainly saturated, with an unusual accumulation (about 45%) of the total fatty acids) of myristic acid. In spite of this, the galactosyldiglycerides contain mainly unsaturated fatty acids. Ninety per cent of the fatty acids of the monogalactosyldiglyceride are unsaturated, including large amounts of alpha-linolenic acid. The ratio of chlorophyll to galactosyldiglyceride content of the cells was remarkably constant at all manganese deficiency levels.
TL;DR: Carbon uptake was recorded in the light for species of the following marine algae: Alaria, Costaria, Desmarestia, Enteromorpha, Gigartina, Nereocystis, Porphyra, and Ulva, which were concluded to use HCO3− ion as a substrate for photosynthesis.
Abstract: Carbon uptake was recorded in the light for species of the following marine algae: Alaria, Costaria, Desmarestia, Enteromorpha, Gigartina, Nereocystis, Porphyra, and Ulva. The change in total inorganic carbon in the experimental water was determined by acid release from 1 ml samples and measured by infrared gas analysis. With the exceptions of Porphyra and Desmarestia, the algae were concluded to use HCO3− ion as a substrate for photosynthesis. The relationship of rate of photosynthesis to total inorganic carbon present in seawater was determined for Ulva fenestrata, Iridaea cordata, and Sargassum muticum.
TL;DR: It is concluded that the inhibition of photosynthesis by ultraviolet irradiation is most likely due to a disruption of the structural integrity of the lamellar membranes which results in the loss of System II activity and associated reactions.