Carbon Dioxide Efflux from Leaves in Light and Darkness

Efflux of carbon dioxide in light and darkness was measured at low ambient CO₂ concentrations in leaves of Rumex acetosa. Light carbon dioxide production (photo-respiration) was found to depend on irradiance and to differ from dark production as to the response to temperature and ambient concentrations of O₂ and CO₂. These observations support previously made suggestions that photorespiration follows a different metabolic pathway to dark respiration.     

Photosynthesis, Respiration and Post-illumination Fixation of CO2 by Corn Leaves as Influenced by Light and Oxygen Concentration

The effect of oxygen concentration on the rate of CO₂-uptake in continuous and intermittent light was studied as well as the CO₂-fixation during a short dark period after light was turned off. In addition the dark respiration and the CO₂-compensation point of attached and detached corn leaves were determined. Leaves of 4 to 22-day old plants were used as experimental material. A closed circuit system of an infrared carbon dioxide analyzer was employed to measure the rate of CO₂-exchange. It was found that in an atmosphere consisting of 100 % oxygen, there was about 50 per cent inhibition of the rate of CO₂-uptake in continuous and intermittent light compared to that in an atmosphere consisting of 21% oxygen. The same was true of the rate of CO₂-fixation in darkness during a short period after the light was turned off. Since the response to oxygen concentration of the CO₂-uptake in light and of the CO₂-fixation in darkness after the light was turned off were similar, it is concluded that the fixation of CO₂ in the short dark period represents an over- shoot of photosynthesis. The rate of dark respiration was little affected by the oxygen concentration in the ranges used in the experiments. The carbon dioxide compensation point which has been observed in leaves of 4 to 14-day old plants was not influenced by either oxygen concentration or light intensity. Since the changes in the rate of CO₂-uptake due to changes in the concentration of oxygen and light intensity had no effect on the CO₂-compensation point, it is concluded that a reabsorption of respiratory CO₂ by photosynthesis could not account for the low value of this point. These results are interpreted as a further corroboration of the statement that the leaves of corn lack the process of photorespiration and that dark respiration is inhibited in light. It was observed that the rate of the CO₂-uptake gradually increased in plants which were from 4 to 22-days old. The inhibitory effect of high concentration of oxygen on the rate of CO₂-uptake was relatively higher in old plants than in young ones.     

Photojet de CO2 et réserves internes en gaz carbonique chez Zea mays

Summary When a leaf of maize (Zea mays) is illuminated following a long enough period of darkness (t10 min) under pure nitrogen, the oxygen evolution occurs only after a lag time from one to several minutes. During this delay, a burst of CO₂ occurs the maximum of which corresponds to the start of oxygen evolution. The source of carbon dioxide is thought to be a stable internal CO₂ reserve which has been previously formed in the leaf and is assumed to be malic acid. For as yet unknown reasons the carbon dioxide issued from the reserve by action of light at the beginning of illumination is not fixed and escapes into the atmosphere; this process could require the phytochrome system.     

Metabolism of <Superscript>14</Superscript>C-glycine as a substrate for photorespiration of the leaf at different developmental stages of ephemeroides

The metabolism of ¹⁴C-glycine (a substrate for photorespiration) was studied in the light and in darkness under natural CO₂ concentration (0.03%) in the leaves of ephemeroides Scilla sibirica Haw. and Ficaria verna Huds. at different developmental stages. Using one and the same sample, potential photosynthesis (at 1% CO₂), true photosynthesis (at 0.03% CO₂), and leaf respiratory capacity were measured by the radiometric and manometric methods, respectively. All measurements were performed at 15°C, an average temperature during ephemer growth. It was found that, in the white zone of the Scilla leaf, the rate of CO₂ evolution resulting from metabolization of exogenous ¹⁴C-glycine was similar in the light and in darkness. In the green zone of the Scilla leaf and in the green leaf of Ficaria, both ¹⁴C-glycine absorption and ¹⁴CO₂ evolution were lower in the light as compared with darkness, which is explained by CO₂ reassimilation. In all treatments of both plant species, a specific inhibitor of glycine decarboxylase complex (GDC), aminoacetonitrile (5 mM) suppressed CO₂ evolution by 20–40%. It was concluded that in ephemeroides mitochondrial GDC, responsible for CO₂ evolution in photorespiration, is formed at the earliest stage of leaf development. This indicates that photorespiration can occur simultaneously with the development of the leaf photosynthetic activity. On the basis of the assumption that carbon losses in the form of CO₂ evolved during photorespiration comprise 25% of true photosynthesis, it was calculated that, in ephemer leaves, the highest rates of photorespiration and photosynthesis were attained during flowering when the leaf area was the largest and the rate of dark respiration was reduced by 1.5–2.0 times. The highest rates of dark respiration were observed in the beginning of growth. In senescing leaves by the end of the plant vegetation, potential photosynthesis and true photosynthesis were reduced, whereas dark respiration remained essentially unchanged. It is concluded that the high rates of potential and true photosynthesis are characteristic of ephemeroides when they complete their short developmental program in early spring (at 15°C); theoretically, photorespiration also occurs at a high rate during this period, when this process provides for a defense against the threat of photoinhibition at low temperature and high insolation.     

Influence of atmospheric oxygen on leaf structure and starch deposition in Arabidopsis thaliana

Plant culture in oxygen concentrations below ambient is known to stimulate vegetative growth, but apart from reports on increased leaf number and weight, little is known about development at subambient oxygen concentrations. Arabidopsis thaliana (L.) Heynh. (cv. Columbia) plants were grown full term in pre-mixed atmospheres with oxygen partial pressures of 2·5, 5·1, 10·1, 16·2, and 21·3 kPa O₂, 0·035 kPa CO₂ and the balance nitrogen under continuous light. Fully expanded leaves were harvested and processed for light and transmission electron microscopy or for starch quantification. Growth in subambient oxygen concentrations caused changes in leaf anatomy (increased thickness, stomatal density and starch content) that have also been described for plants grown under carbon dioxide enrichment. However, at the lowest oxygen treatment (2·5 kPa), developmental changes occurred that could not be explained by changes in carbon budget caused by suppressed photorespiration, resulting in very thick leaves and a dwarf morphology. This study establishes the leaf parameters that change during growth under low O₂, and identifies the lower concentration at which O₂ limitation on transport and biosynthetic pathways detrimentally affects leaf development.     

The Germination of Avena fatua under Different Gaseous Environments

The atmosphere in which seeds germinate can profoundly affect the level of germination and dormancy. Seeds were germinated in atmospheres containing various concentrations of carbon dioxide and oxygen. At the same time the effect of light on these systems was examined. The germination of partially dormant populations of wild oat seed is inhibited by white light. This response to light is most apparent when the curyopsis is enclosed in the pales. Investigations into the effect of the ambient atmosphere on germination have indicated that, while oxygen is a necessary factor in the germination of tliis species, carbon dioxide also has an effect. A lack of carbon dioxide increases the degree of light inhibition of germination; 3 per cent carbon dioxide (by volume) allows germination in light; 20 per cent carbon dioxide inhibits germination in light and darkness at all tested oxygen concentrations.     

Photosynthesis, Photorespiration and Respiration of Detached Spruce Twigs as Influenced by Oxygen Concentration and Light Intensity

The effects of oxygen concentration and light intensity on the rates of apparent photosynthesis, true photosynthesis, photorespiration and dark respiration of detached spruce twigs were determined by means of an infra-red carbon dioxide analyzer (IRCA). A closed circuit system IRCA was filled with either 1 per cent of oxygen in nitrogen, air (21 % O₂) or pure oxygen (100 % O₂). Two light intensities 30 × 10³ erg · cm ^?2· s^?1 and 120 × 10³ erg · cm^?2· s^?1 were applied. It has been found that the inhibitory effect of high concentration of oxygen on the apparent photosynthesis was mainly a result of a stimulation of the rate of CO₂ production in light (photorespiration). In the atmosphere of 100 % O₂, photorespiration accounts for 66–80 per cent of total CO₂ uptake (true photosynthesis). Owing to a strong acceleration of photorespiration by high oxygen concentrations, the rate of true photosynthesis calculated as the sum of apparent photosynthesis and photorespiration was by several times less inhibited by oxygen than the rate of apparent photosynthesis. The rates of dark respiration were essentially unaffected by the oxygen concentrations used in the experiments. An increase in the intensity of light from 30 × 10³ erg · cm^?3· s^?1 to 120 · 10³ erg · cm^?2· s^?1 enhanced the rate of photorespiration in the atmospheres of 21 and 100 % oxygen but not in 1 % O₂. The rate of apparent photosynthesis, however, was little affected by light intensity in an atmosphere of 1 % oxygen.     

Influence of Inorganic Phosphate on Photosynthesis of Wheat Chloroplasts: II. RIBULOSE BISPHOSPHATE CARBOXYLASE ACTIVITY

Isolated wheat chloroplasts were pre-incubated in the dark inthe presence of various concentrations of inorganic phosphatewith or without carbon dioxide, oxaloacetate, glycerate, and3-phosphoglycerate. The effect of subsequent illumination onphotosynthetic oxygen evolution, ribulose bisphosphate carboxylaseactivity, ATP content, and ribulose bisphosphate content wasinvestigated. Inorganic phosphate had little effect on ribulosebisphosphate carboxylase activity in darkness or during theinitial phase of illumination, but it prevented the declinein activity that occurred during later stages of illumination,when photoreduction of CO₂ was decreasing in rate. Additionof inorganic phosphate to chloroplasts illuminated without phosphaterestored the ribulose bisphosphate carboxylase activity, increasedthe ATP, and decreased the ribulose bisphosphate in the organelles.The responses to CO₂, oxaloacetate, glycerate, and 3-phosphoglyceratesuggest that the decreased activity of ribulose bisphosphatecarboxylase during photosynthesis results from ATP consumption. Purified ribulose bisphosphate carboxylase was activated byinorganic phosphate, but this activation did not occur in thepresence of ATP. ATP inhibited ribulose bisphosphate carboxylasewhen it was present in combination with various photosyntheticmetabolites. Inactivation of ribulose bisphosphate carboxylase in chloroplasts,illuminated in the absence of inorganic phosphate, is not dueto lack of activation by inorganic phosphate or ATP. It mayresult from decreased stromal pH. Key words: Ribulose bisphosphate carboxylase, Chloroplasts, Wheat, Phosphate, ATP     

About effect of processes in the earth crust on evolution of photosynthesis (as indicated by data on carbon isotopic composition)

A probable mechanism of effect of processes occurring in the Earth crust on evolution of photosynthesis is considered. According to the hypothesis, this effect is realized through entrance to the Earth atmosphere of carbon dioxide that stimulates photosynthesis. Supply of CO₂ is irregular and is due to irregular movements of the Earth crust plates. This is accompanied by destruction of carbonates and conversion of carbon of the organic matter to CO₂ due to processes of reduction of sulfates. The CO₂ content in atmosphere rises for relatively short orogenic periods, due to intensive crust plate movement, while for the subsequent long periods, called the geosynclinal ones, of the relatively slow plate movement, the CO₂ content falls due to the higher rate of its consumption for photosynthesis. Owing to the carbon isotopic fractionation accompanying photosynthesis, regular isotopic differences appear between the atmospheric CO₂ and the “living” matter (Relay’s effect); these differences are then transformed to isotope differences of the carbonate and organic carbon. At the appearance in atmosphere of free oxygen-product of photosynthesis-in organisms there appears photorespiration that also is accompanied by fractionation of carbon isotopes, but with effect of opposite sign. This leads to enrichment of the photosynthesizing biomass with ¹³C isotope at the orogenic periods. As a result, the initially pronounced isotope differences of the carbonate and organic carbon decrease by the end of the geosynclinal periods. According to the proposed model, concentrations of CO₂ and O₂ are exchanged in the antiphase. They lead to alternation of periods of warning up and cooling off on the Earth. The former coincide with the orogenic periods, the latter appear at the end of geosynclinal periods when in atmosphere there is accumulated oxygen, while in sediments-organic substance. The accumulation of organic substance leads to formation of petroleum-maternal masses. To substantiate the model, data on isotope composition of carbon of carbonate and organic substance of rocks are used and its ability to explain several known natural regularities and empirical correlations. The model is used for analysis of some key stages of evolution of photosynthesis.     

Chlorophyll formation and the development of photosynthesis in illuminated etiolated pea leaves

Summary The protein synthesis inhibitors chloramphenicol and terramycin, and light of low intensity were used to retard the rate of chlorophyll formation in illuminated dark grown pea leaves. In the control leaves the onset of photosynthesis, as measured by carbon dioxide exchange of the whole leaves, and reduction of ferricyanide and metmyoglobin and photo-oxidation of ascorbate in isolated chloroplasts, was observed after 2–4 hours illumination. The photosynthetic activity of the treated leaves did not commence until 10–12 hours illumination had elapsed. In both the control and treated leaves the onset of photosynthesis occurred when the total chlorophyll content was 0.04 mg/g fresh weight. The precise point of photosynthetic inception was apparently more related to the attainment of a specific total chlorophyl content than to the ratio of chlorophyll a to chlorophyll b. A marked increase in the evolution of carbon dioxide in the light was observed in the treated leaves during the first 10 hours of greening. This observation could not be ascribed to photorespiration since the leaves did not possess an active photosystem. It is suggested that the enhanced respiration may have been due to the light-induced activation of synthetic pathways responsible for the formation of chloroplast constituents.The following abbreviations are used CMU 3(3-chlorophenyl)-1, 1-dimethylurea - DCIP dichlorophenol indophenol - PMS phenazine methosulphate - TRIS 2-amino-2-hydroxymethyl propane-1, 3-diol This work was supported by a Science Research Council studentship granted to R. J. Dowdell and submitted for the degree of Ph. D. of Bath University of Technology.     

Effect of O2:CO2 ratio on the primary metabolism of Chlamydomonas reinhardtii

High oxygen:carbon dioxide ratios may have a negative effect on growth and productivity of microalgae. To investigate the effect of O₂ and CO₂ concentrations and the ratio between these on the metabolism of Chlamydomonas reinhardtii we performed turbidostat experiments at different O₂:CO₂ ratios. These experiments showed that elevated O₂ concentrations and the corresponding increase in the ratio of O₂:CO₂ common in photobioreactors led to a reduction of growth and biomass yield on light with 20–30%. This is most probably related to the oxygenase activity of Rubisco and the resulting process of photorespiration. Using metabolic flux modeling with measured rates for each experiment we were able to quantify the ratio of the oxygenase reaction to the carboxylase reaction of Rubisco and could demonstrate that photorespiration indeed can cause the reduction in biomass yield on light. The calculated ratio of the oxygenase reaction to the carboxylase reaction was 16.6% and 20.5% for air with 2% CO₂ and 1% CO₂, respectively. Thus photorespiration has a significant impact on the biomass yield on light already at conditions common in photobioreactors (air with 2% CO₂). Biotechnol. Bioeng. 2011;108: 2390–2402. © 2011 Wiley Periodicals, Inc.     

Photosynthesis by isolated chloroplasts, simultaneous measurement of carbon assimilation and oxygen evolution

Photosynthetic carbon assimilation by isolated chloroplasts and its associated oxygen evolution were measured simultaneously in a single simplified reaction mixture. Each showed an initial lag prior to the attainment of the maximal rate and the photosynthetic quotient was unity during the period of illumination. Following illumination an oxygen uptake was observed in the dark which was not accompanied by any net release of newly fixed carbon dioxide.     

The mode of action of insecticidal controlled atmospheres

Arthropods cope with reduced oxygen and elevated carbon dioxide atmospheres with a reduction in metabolic rate, also called metabolic arrest. The reduction in metabolism lessens the pressure on the organism to initiate anaerobic metabolism, but also leads to a reduction in ATP production. The natural permeability of cellular membranes appears to be important for the survival of the arthropod under low oxygen or high carbon dioxide atmospheres. Despite the similarities in response, arthropod mortality is generally greater in response to high carbon dioxide as apposed to low oxygen atmospheres. There appears to be a greater decrease in ATP and energy charge in arthropods exposed to high carbon dioxide as compared with low oxygen atmospheres, and this may be due to greater membrane permeability under carbon dioxide leading to an inefficient production of ATP. Reduced oxygen and elevated carbon dioxide atmospheres can have an additive effect in some cases, depending on the concentrations used. The effect of these atmospheres on arthropods depends also on temperature, species and life stage. Additional work is needed to fully understand the mode of action of controlled atmospheres on arthropod pests.     

Effect of oxygen on photosynthesis, photorespiration and respiration in detached leaves. I. Soybean

The effect of O₂ on the CO₂ exchange of detached soybean leaves was measured with a Clark oxygen electrode and infrared carbon dioxide analysers in both open and closed systems.

The rate of apparent photosynthesis was inhibited by O₂ while the steady rate of respiration after a few minutes in the dark was not affected. Part of the inhibition of apparent photosynthesis was shown to be a result of increased photorespiration. This stimulation of photorespiration by O₂ was manifested by an increase in the CO₂ compensation point.

The differential effects of O₂ on dark respiration (no effect) and photorespiration (stimulation) indicated that these were 2 different processes.

Moreover the extrapolation of the CO₂ compensation point to zero at zero O₂ indicated that dark respiration was suppressed in the light at least at zero O₂ concentration.

     

A Study of the Growth and Photoperceptivity of Etiolated Oat Seedlings

The photoperceptivity of intact oat seedlings has been observedafter pretreating them for 3 days in darkness with a numberof substances—copper and manganese ions, EDTA, copper-glycine,glycine, nitrates, indoleacetic acid, ethanol, and carbon dioxide. None enhanced photosensitivity; carbon dioxide and ethanol reducedit. Copper-glycine in darkness promoted mesocoty1 growth and inducedroot formation. The effects of carbon dioxide and ethanol are shown to be identicaland to account for this a speculative proposal is made aboutmaturation. An alternative explanation of the growth of the mesocotyl thenarises. The relationship between maturation and the behaviour of theseedling upon illumination is discussed.     

Effect of Oxygen on Photosynthesis, Photorespiration and Respiration in Detached Leaves. II. Corn and other Monocotyledons

The effect of O₂ on the CO₂ exchange of detached leaves of corn (Zea mays), wheat (Triticum vulgare), oats (Avena sativa), barley (Hordeum vulgare), timothy (Phleum pratense) and cat-tail (Typha angustifolia) was measured with a Clark oxygen electrode and infrared carbon dioxide analysers in both open and closed systems.

Corn leaves did not produce CO₂ in the light at any O₂ concentration, as was shown by the zero CO₂ compensation point and the absence of a CO₂ burst in the first minute of darkness. The rate of photosynthesis was inhibited by O₂ and the inhibition was not completely reversible. On the other hand, the steady rate of respiration after a few minutes in the dark was not affected by O₂.

These results were interpreted as indicating the absence of any measurable respiration during photosynthesis. Twelve different varieties of corn studied all responded to O₂ in the same way.

The other 5 monocotyledons studied did produce CO₂ in the light. Moreover, the CO₂ compensation point increased linearly with O₂ indicating a stimulation of photorespiration.

The implications of the lack of photorespiration in studies of primary productivity are discussed.

     

A closed system for measurement of photosynthesis,photorespiration and transpiration rates

An installation is described enabling measurements of photosynthesis, transpiration and dark respiration, and estimation of photorespiration rates at different carbon dioxide and oxygen concentrations, at different irradiances and leaf temperatures.     

Photorespiration and Glycolate Metabolism: A Re-examination and Correlation of Some Previous Studies

Some previous studies of photorespiration and glycolate oxidation were re-examined and correlated by infra-red CO₂ analysis. Data about rate of photosynthesis and oxygen sensitivity indicated that complete inhibition of photosynthesis with 3-(3,4-dichlorophenyl)-1,1 dimethyl urea (DCMU) allowed dark respiration to continue in the light. Photorespiration was also inhibited. The oxygen sensitivity of glycolate-stimulated CO₂ production was found to be compatible with the proposal that glycolate is a substrate of photorespiration. Both `in vivo' and `in vitro' studies of the alga Nitella flexilis have revealed a pathway of glycolate oxidation similar to that of higher plants. DCMU inhibition of photosynthesis by Nitella gave results similar to those for the monocotyledons tested. Under very low light intensity, carbon dioxide compensation in corn was measurable but was not sensitive to high oxygen concentration. It appears that the lack of photorespiration in this plant is not the end result of efficient internal recycling of CO₂ to photosynthesis.     

Primary Photosynthetic Induction Phenomena in Wheat

The induction phenomena of photosynthesis in leaves of wheat were studied with a Beckman oxygen sensor. By special treatment prior to illumination, e.g. long dark and anaerobic periods the oxygen evolution could be divided into two parts, one consisting of two or three transients appearing under the first minute of illumination and one consisting of the main oxygen evolution. One or two transients could be observed when the plant was placed in darkness after an illumination period. The oxygen evolution had the same appearance in monochromatic as in white light. KCN-treatment inhibited only the main oxygen evolution. The transients are interpreted as being manifestations of the primary processes connected with the start of photosynthesis. The main oxygen evolution is assumed to be closely related to the processes connected to the Calvin-cycle. Experiments were also performed to ascertain that the observed induction phenomena were not connected with the stomatal movements in the leaves.     

Engineering analysis of the high-density heterotrophic cultivation of mung bean sprouts

This study investigated the heterotrophic growth behavior of mung beans cultivated in an individual bed under water supply. The fresh weight of mung beans in the bed was estimated, and changes in temperature, and oxygen and carbon dioxide concentrations were recorded during the cultivation period. The specific growth rate, oxygen uptake rate, and carbon dioxide evolution rate, based on the fresh weight in the bed, were calculated. Growth under heterotrophic cultivation can be classified into the following three stages. Reductions in specific oxygen uptake rate, specific carbon dioxide evolution rate, and specific energy production rate corresponded to that of specific growth rate. Indicators of biological activity related to oxygen and carbon dioxide were evaluated quantitatively for beds under high-density heterotrophic cultivation. Moreover, the results obtained from this study successfully demonstrate that there is a relationship between the growth of mung beans and indicators of biological activity.