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

Downton, W. J. S.; Tregunna, E. B.

doi:10.1104/pp.43.6.923

Cited by 50 publications

(19 citation statements)

References 28 publications

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“…The accelerated respiration of serine, glucose, and potassium acetate was less than that of the attached leaf. Surprisingly, the stimulation of CO2 efflux of maize by glycolic acid in my experiments exceeded the stimulation previously found for tobacco, wheat, and oats (4,15), all species presumably using glycolic acid as a substrate of photorespiration.…”

Section: Methodscontrasting

confidence: 50%

Postillumination Respiration of Maize in Relation to Oxygen Concentration and Glycolic Acid Metabolism

Heichel¹

1972

Plant Physiol.

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Prior illumination in C02-free air enhances a respiration from maize (Zea mays L.) leaves different in onset and duration from the postillumination burst of photorespiration. Respiration of attached leaves during the dark-light-dark sequence of the experiment was measured by infrared gas analysis of CO2 efflux from leaves at 25 ± 1 C into CO2-free N2 containing 0.04%, 2.23%, or 40% 02, or into C02-free air in an acrylic plastic chamber. Rapid flushing at 10 1 min-' replaced air by other gas mixtures.Respiration of excised leaves was measured as outlined above except for the following changes. Leaves were excised from the plant and recut beneath air-free distilled H20 in a beaker resting on the pan of a balance. The leaf was sealed into the chamber with the cut end of the leaf suspended in the beaker so that movement of solution into the leaf could be continuously monitored. In leaf-feeding experiments, the rates of respiration and steady transpiration were first established with the leaf in distilled H20, and before illumination the H20 was quickly replaced with 50 mm solutions of metabolites or with solutions containing the inhibitors HPMS1 or CMU. After illumination the pattern of respiration caused by each metabolite was then established using the protocol developed for attached leaves. During the respiration of some compounds. the 02 concentration was altered as previously described for attached leaves.The total volume of the heat exchange unit and chamber was 8.4 liters, giving a volume to leaf area ratio of approximately 20 cm2 cm-2. Relative humidity was 50 ± 5% during the experiments. Leaves were usually illuminated for 20 min at 0.38 cal cm-2 min-' (400-700 nm) during the dark-light-dark sequence to provide energy to stimulate influx of solutions of metabolites and respiration in the subsequent dark period. To measure the response to light of CO2 efflux during the illumination, illumination was attenuated with successive layers of

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Section: Methodscontrasting

confidence: 50%

Postillumination Respiration of Maize in Relation to Oxygen Concentration and Glycolic Acid Metabolism

Heichel¹

1972

Plant Physiol.

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“…Some data are available to indicate that dark respiration may be suppressed in the light (24) but there is also evidence, based on the metabolism of "C-labeled intermediates, that shows that the dark respiration pathways continue to function in the light (19,29). There does not appear to be a direct effect of light on dark respiration in leaves as the rate is not affected by light when photosynthesis is suppressed by lack of chlorophyll (22) or by inhibitors (10,11). Thus in the absence of definitive evidence that dark respiration is inhibited it seems reasonable to assume that it continues.…”

Section: '180 200mentioning

confidence: 99%

The Rate of Photorespiration during Photosynthesis and the Relationship of the Substrate of Light Respiration to the Products of Photosynthesis in Sunflower Leaves

1971

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Single attached leaves of sunflower (Helianthus annus L."Mennonite") were supplied "CO2 of constant specific radioactivity in gas mixtures containing various CO2 and 02 concentrations. The "CO2 and C02 fluxes were measured concurrently in an open system using an ionization chamber and infrared gas analyzer.The rate of photorespiration (5.7 + 0.3 mg CO2-dm 2 hr-') during photosynthesis in 21% 02 at 25 C and 3,500 footcandles was over three times the rate of dark respiration and was independent of C02 concentrations from 0 to 300 Al/l.The steady rate of C02 evolution into CO2-free air was about 30% lower. Low oxygen (1%) inhibited both "CO2 and C02 evolution, both during photosynthesis and in CO2-free air in the light.At 300 ul/l C02 apparent photosynthesis was inhibited 41% by 21% 02. Two-thirds of the inhibition was due to the inhibition of true photosynthesis by oxygen and one-third due to the stimulation of photorespiration. At 50 u1d/l C02, where the percentage inhibition of apparent photosynthesis by 21% oxygen was 92 %, photorespiration accounted for two-thirds of the total inhibition.The rate of 14CO2 uptake by the leaf decreased about 30 seconds after the introduction of 14CO2, indicating that "4CO2 was rapidly evolved from the leaf. The rate of "CO2 evolution increased rapidly with time, the kinetics depending on the C02 concentration. The high specific radioactivity of the "4CO2 evolved during photosynthesis or in the early period of flushing in C02-free air showed that the substrate for light respiration was an early product of photosynthesis. From the measurement of "CO2 and C02 evolution into C02-free air over a longer time period it was apparent that at least three compounds, each of deereased 1"C content, could supply the substrate for light respiration.Based on a consideration of the specific radioactivity of There is now much evidence to show that the rate of CO, evolution from green leaves in the light exceeds that of dark respiration and that the substrate and mechanism of CO2 evolution in the light are different from those of CO-evolution in the dark (24). All methods to date (23, 24, 38), however, have not measured the rate of photorespiration under conditions of steady state photosynthesis nor have they (18, 38) allowed a continuous measurement of the specific radioactivity of the 'CO. evolved from a leaf during or after a period of photosynthesis in 'CO2. We have recently described a system (26) which continuously measures the CO. or "CO2 fluxes from leaves. In this paper we present results on the rates of photorespiration duLring steady state photosynthesis and on the relationship of the "CO2 evolved to the products of "CO2 fixation. Brief accounts of this work have previously been presented (27,28). MATERIALS AND METHODSThe mnaterials and methods have been fully described in a preceding paper (26). Sunflower leaves (Helianthlls annulis L."Mennonite"), grown as previously described (26), were used for all experiments. RESULTSFrom the CO; and "CO2 uptake and the average specific ...

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“…Ribulose-1 , 5-diP carboxylase was assayed according to Bjorkman (5 (10) with the Clark electrode. The reaction was initiated by adding 10 .moles of sodium glycolate in 0.2 ml of the phosphate buffer to 2.8 ml of the enzyme preparation. Controls were samples to which no glycolate was added.…”

Section: Materials and Miethodsmentioning

confidence: 99%

Photosynthesis and Photorespiration in Typha latifolia

McNaughton

Fullem

1970

Plant Physiol.

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NaH'4CO3 (105 Cpm) to 1.3 ml of the enzyme preparation. At intervals, 0.4-ml samples were removed and acidified with 0.1 ml of 6 N acetic acid. Controls consisted of a zero time sample that was acidified immediately upon mixing the reaction components, and a reaction mixture lacking ribulose-1, 5-diP which was acidified at the end of the experimental period. The same enzyme preparation procedure was used for phosphopyruvate carboxylase except that dithioerythritol was sometimes substituted for reduced glutathione to provide an alternative test for sulfhydryl protection. The assay system for this enzyme, after Slack and Hatch (25), contained 1.55 ,umoles of phosphopyruvate and 15 ,umoles of sodium glutamate in substitution for the ribulose-1,5-diP used above. Controls were the same. For the assay of glycolate oxidase activity, leaves were homogenized in 0.067 M phosphate buffer (pH 7.8) and filtered through four layers of 60 mesh cheesecloth. This homogenate was used directly in a polarographic assay (10) with the Clark electrode. The reaction was initiated by adding 10 .moles of sodium glycolate in 0.2 ml of the phosphate buffer to 2.8 ml of the enzyme preparation. Controls were samples to which no glycolate was added. Addition of the enzyme cofactor, flavin mononucleotide, was not found to be stimulatory, and this was omitted from the assay system. Reagents were from Sigma.For "4CO0 assimilation experiments, leaves were preilluminated in 2 X 106 ergs cm-2 sec-l of light with their base in distilled water or a glycolate oxidase inhibitor, 0.01 M a-hydroxypyridinemethanesulfonic acid (Aldrich), for 30 min prior to release of "4CO2 by the acidification of a bicarbonate solution. Carbon dioxide concentration was 370 ,ul liter-' after addition of bicarbonate, to eliminate artifacts arising from high CO2 concentrations. Following 10 min of photosynthesis with water or 20 min with the inhibitor, the leaves were killed with boiling 80%-ethanol. In the controls, 1.8 AC of "CO, were used. In the experiments with inhibitor, 2.02 ,C of "CO2 were used. The different time periods and specific radioactivities of "CO2 were used to assure that approximately the same amount of radioactivity would be recovered from chromatograms of both treatments without overloading with plant extracts. Total cpm recovered from chromatograms per g of leaf extracted were 43,200 + 21,600 (0.95 confidence interval) for the water controls and 53,600 + 8,300 for experiments in inhibitor. For

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

Cited by 50 publications

References 28 publications

Postillumination Respiration of Maize in Relation to Oxygen Concentration and Glycolic Acid Metabolism

Postillumination Respiration of Maize in Relation to Oxygen Concentration and Glycolic Acid Metabolism

The Rate of Photorespiration during Photosynthesis and the Relationship of the Substrate of Light Respiration to the Products of Photosynthesis in Sunflower Leaves

Photosynthesis and Photorespiration in Typha latifolia

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