The effect of oxygen on the reduction of CO2 to glycolic acid and other products during photosynthesis by Chlorella

Bassham, James A.; Kirk, Martha

doi:10.1016/0006-291x(62)90019-0

Cited by 87 publications

(32 citation statements)

References 19 publications

(10 reference statements)

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“…Glv colic acid, as well as being ubiquitous in leaves, is one of the earliest products of photosynthesis particularly at lower CO., concentrations and higher O. concentrations (1,2,11,20,30). In addition, Ludwig and Krotkov (13) have provided evidence for some early photosynthetic product being oxidized to CO., in light.…”

Section: Resultsmentioning

confidence: 96%

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

Downton

Tregunna

1968

Plant Physiol.

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A bstract. Some previous studies of photorespiration and glycolate oxidation were reexamined and correlated by infra-red CO, 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 senisitivity of glycolate-stimulated CO2 production was found to be compatible with the proposal that glycolate is a substrate of photorespiration. B-oth '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 CO, to photosynthesis.Photorespiration has been described as a CO, producing process that operates during photosynthesis in some leaves and algae. The newer evidence supporting this concept is based on the response of photorespiration to 0. concentration. It has been shown that dark respiration in leaves is saturated by about 2 % 02 whereas photorespiration has a much higher 0., requirement (7,25). 'Much recent literature also implicates glycolic acid as a substrate of photorespiration. The correlation which we have studied is the O., requirement for glycolate-stimulated CO, production. These results led to another studv of whether corn leaves produce CO., by photorespiration during photosynthesis.A recent paper by El-Sharkawy et al. (6) has provided data on CO. production in the light and dark when C0, source-sink relationships were changed by inhibiting photosynthesis with DCM\IU.Under these conditions the rates in light and dark were identical and these data were used as evidence for a common source of CO, evolved both during photosynthesis and in the dark. We re-examined this work and extended it with information about the effect of 02 tension on rates of CO., production.As a check against the possibility that the gas exchange results from the DCMU-treated monocotyledons were an artifact of stomatal behavior, the gas exchange of a DCMU-treated alga, Nitella flexilis, was studied. This alga has been shown to have a photorespiratory mechanism similar to that of some land plants (3). Results obtained by inhibiting photosynthesis by non-chemical means have

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Section: Resultsmentioning

confidence: 96%

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

Downton

Tregunna

1968

Plant Physiol.

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“…In addition to the Calvin cycle, the data for malate and PEP in Figure 5 suggests a ,-carboxylation system leading eventually to malate. The PEPcarboxylating enzyme evidently does not require light activation, as does the RuDP-carboxylating enzyme (13) (3,14). The (7,18,21).…”

Section: Discussionmentioning

confidence: 99%

Intermediates Of Photosynthesis in Acetabularia mediterranie Chloroplasts

1970

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The chloroplast fraction isolated from Acetabularia mediterranie was exposed to 14CO2 as NaH'4C03 in light and darkness, and soluble radioactive compounds were analyzed at frequent intervals. The behavior of Calvin cycle intermediates on the chloroplasts isolated from 2 to 3 g of cells, about 2 cm long, each preparation containing 600 to 750 j,g of total chorophyll (1). The chloroplasts were suspended in 5 ml of the A medium described earlier (6), except that the pH was reduced to 7.2 in order to reduce the equilibrium bicarbonate concentration of the medium (15). As a result, the bicarbonate concentration was low enough that it probably became rate-limiting after about 10 min of photosynthesis (6), but it ensured maximum specific activity of fixed 4CO2 .Experimental. Chloroplast preparations were illuminated by fluorescent lights (2500 ft-c), and 100 ,uc of NaH14CO3 (specific radioactivity about 40 mc/mmole) were added. Sampling began immediately. Samples of 25 Al were withdrawn with a Schwartz Biopette automatic pipette and were quickly applied to the corner of 8-inch X 11-inch chromatography sheets (Whatman 3MM). These were immediately placed in liquid nitrogen until the end of the experiment (30-60 min). A few chromatograms were made with 50 or 100 ,ul. These did not have any spots which could not be seen on the 25 Al chromatograms, showing that all major compounds were being detected. With this technique, samples could be taken at intervals as short as 8 sec, although the sample size was apt to be erratic because of pipetting errors at this speed. Much of this problem was later eliminated by cutting the tips of the polyethylene pipettes at a sharp angle. Samples taken at longer intervals were in close agreement. The time from withdrawal of the sample to the freezing of the chromatograms was about 4 sec. In the dark fixation experiment (Table I), all conditions and procedures were identical except that the experiment was run in darkness.Chromatography and Radioautography. At the conclusion of the experiment chromatograms were removed singly from the liquid nitrogen, and the origins were fixed by 1-to 2-min exposure to the hot vapors of vigorously boiling ethanol. This procedure avoids the problems of extraction and concentration and reduces the nonbiological breakdown of labile intermediates to a minimum (5). Two-dimensional chromatograms were run in 80% phenol at pH 5.4 and butanol-acetic acid-water (12:3:5) and radioautographed. Representative radioautographs are shown in Figure 1. The spots were cut out and counted on both sides in an ultrathin window gas flow Geiger-Mueller counter. The counts from both sides were averaged (4) and corrected for coincidence. All results are presented as counts per minute per sample as determined from a 25 MAl chromatogram, and they are strictly comparable within each experiment. The sum of radioactivities of all the compounds that moved from the origin was called "soluble radioactivity," and the radioactivity which did not move from the origin was termed "insolu...

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“…A major part of this variability is apparently due to plant to plant differences and is inherent in single leaf determinations. (2) and oxidation (15), while the constant serine pool indicates that multiple serine pools exist. Servaites and Ogren (33) also found evidence for a serine pool in soybean leaf cells which is not available for metabolism through the glycolate pathway.…”

Section: Co2 Exchangementioning

confidence: 99%

“…The 02 competition with CO2 on RuBP carboxylase has been used to explain the direct inhibition of CO., fixation by 02 (20,26). Although the competitive effect of CO) on the oxygenation reaction and, therefore, on glycolate production is well known at CO2 concentrations near or above 1,000 1l/I (2,35), the extent of labeling in glycolate pathway intermediates (27,34), the rate of carbon flux through the pathway (24), and the photorespiration rate (23) all remain nearly constant with decreasing CO2 concentrations below 400,il/l.…”

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confidence: 99%

Oxygen and Carbon Dioxide Effects on the Pool Size of Some Photosynthetic and Photorespiratory Intermediates in Soybean (Glycine max [L.] Merr.)

Hitz¹,

Stewart²

1980

Plant Physiol.

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The levels of ribulose 1,5-bisphosphate (RuBP), 3-phosphoglyceric acid (PGA), glycolate, glycine, and serine were measured in soybean leaflets during photosynthesis in atmospheres ranging from 1 to 60% 02 and from 0 to 500 microliters per liter CO2.The RuBP level remained constant as CO2 concentration was decreased in atmospheres containing 20 or 60% 02, but increased as CO2 concentration was decreased in atmospheres containing 1% 02. PGA on RuBP carboxylase has been used to explain the direct inhibition of CO., fixation by 02 (20,26). Although the competitive effect of CO) on the oxygenation reaction and, therefore, on glycolate production is well known at CO2 concentrations near or above 1,000 1l/I (2, 35), the extent of labeling in glycolate pathway intermediates (27, 34), the rate of carbon flux through the pathway (24), and the photorespiration rate (23) Intact leaves apparently import carbon into the Calvin cycle and subsequently into the glycolate pathway during photosynthesis in O2 at low CO2 concentration. The specific radioactivity of evolved CO2 (23) and of some glycolate pathway intermediates (24) remains less than that of the fed "CO2 at air levels of 02 and CO2 concentrations below 400 M1/1. If all photorespiratory CO2 arises from the glycolate pathway, this result is most simply explained by a flux of stored carbohydrate into the Calvin cycle and glycolate pathway during photorespiratory CO2 loss (23). Loss of 14C from sucrose-and starch-containing fractions during illumination of C3 leaves in C02-free 02 has also been shown (21), and the specific activity of CO2 evolved into C02-free air after periods of 14CO2 fixation declines more rapidly than the rate of CO2 evolution (7,17). Chloroplasts in the intact leaf may thus be supplied with a carbon source to maintain the level of Calvin cycle intermediates even at low CO2 concentration.To determine whether or not the loss of photorespiratory CO2 at CO2 concentrations near or below the CO2 compensation point is sufficient to reduce the level of Calvin cycle and glycolate pathway intermediates, we have measured the steady-state photosynthesis pool sizes of RuBP, PGA, glycolate, glycine, and serine. Pool size measurements were made at three 02 concentrations and CO2 concentrations varying from 0 to 500 tlI/l. Net CO2

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The effect of oxygen on the reduction of CO2 to glycolic acid and other products during photosynthesis by Chlorella

Cited by 87 publications

References 19 publications

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

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

Intermediates Of Photosynthesis in Acetabularia mediterranie Chloroplasts

Oxygen and Carbon Dioxide Effects on the Pool Size of Some Photosynthetic and Photorespiratory Intermediates in Soybean (Glycine max [L.] Merr.)

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