Effect of Light on the Tricarboxylic Acid Cycle in Scenedesmus

Marsh, H. V.; Galmiche, J.M.; Gibbs, Martin

doi:10.1104/pp.40.6.1013

Cited by 64 publications

(26 citation statements)

References 16 publications

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“…If the mitochondria are functional in the light (27), the pyruvate would be utilized by the Krebs cycle system with the production of ATP, C02, and organic acids. However, if the mitochondria are not functional in the light, the glycolytic sequence could terminate with the formation of 3-PGA.…”

Section: Resultsmentioning

confidence: 99%

Generation of Reduced Nicotinamide Adenine Dinucleotide for Nitrate Reduction in Green Leaves

1971

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An in vivo assay of nitrate reductase activity was developed by vacuum infiltration of leaf discs or sections with a solution of 0.2 M KNO3 (with or without phosphate buffer, pH 7.5) and incubation of the infiltrated tissue and medium under essentially anaerobic conditions in the dark. Nitrite production, for computing enzyme activity, was determined on aliquots of the incubation media, removed at intervals.By adding, separately, various metabolites of the glycolytic, pentose phosphate, and citric acid pathways to the infiltrating media, it was possible to use the in vivo assay to determine the prime source of reduced nicotinamide adenine dinucleotide (NADH) required by the cytoplasmically located NADH-specific nitrate reductase. It was concluded that sugars that migrate from the chloroplast to the cytoplasm were the prime source of energy and that the oxidation of glyceraldehyde 3-phosphate was ultimately the in vivo source of NADH for nitrate reduction.This conclusion was supported by experiments that included: inhibition studies with iodoacetate; in vitro studies that established the presence and functionality of the requisite enzymes; and studies showing the effect of light (photosynthate) and exogenous carbohydrate on loss of endogenous nitrate from plant tissue.The level of nitrate reductase activity obtained with the in vitro assay is higher (2.5-to 20-fold) than with the in vivo assay for most plant species. The work done to date would indicate that the in vivo assays are proportional to the in vitro assays with respect to ranking genotypes for nitrate-reducing potential of a given species. The in vivo assay is especially useful in studying nitrate assimilation in species like giant ragweed from which onlv traces of active nitrate reductase can be extracted.indirectly via oxidation of carbohydrates produced photosynthetically. Work with illuminated algae and Perilla (42,9,20) suggests that carbohydrate oxidation is directly involved in nitrate reduction and thus would be similar to the process operative in nonchlorophyllous tissue (45). In contrast, Mendel and Visser (28) deduced from studies with 15N-nitrate using tomato leaves that nitrate reduction and assimilation was dependent on respiratory (mitochondrial) energy in the dark while a separate light-dependent pathway was operative with illumination. The isolation of a NAD(P)H-nitrate reductase from soybean leaves and the demonstration that a reconstituted system of enzyme, grana, and NADP when illuminated would reduce nitrate seemed to establish the coupling of light via an electron transport system to nitrate reduction (11). Doubt was cast upon this conclusion by the subsequent findings that nitrate reductase in leaf tissue (including soybeans) is NADHdependent (2, 3, 44), nitrate reductase is localized in the cytoplasm and not within the chloroplasts (34, 36), and pyridine nucleotides do not readily migrate from the chloroplasts (18,31). In contrast, several photosynthetic metabolites (3-PGA, 3-PGAId, 3-DHAP, and RDP are most mobile)3 mig...

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Section: Resultsmentioning

confidence: 99%

Generation of Reduced Nicotinamide Adenine Dinucleotide for Nitrate Reduction in Green Leaves

1971

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“…by volume of C02. We have assumed that light has no effect on the turnover of the tricarboxylic acid cycle, as shown by Marsh, Galmiche, and Gibbs (1965), and Anderson and Fuller (1967) and that the enhancement of net photosynthesis in the absence of oxygen is largely due to the inhibition of photorespiration, as suggested by Jolliffe and Tregunna (1968). However, the presence of oxygen may also inhibit cyclic electron flow in photosynthesis (Heber 1969).…”

Section: Methodsmentioning

confidence: 99%

Photosynthesis and Respiration by the Flag Leaf and Components of the Ear During Grain Development In Wheat

Evans¹,

Rawson²

1970

Aust. Jnl. Of Bio. Sci.

209

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SummaryRates of photosynthesis and dark respiration of the ears and flag leaves of three varieties of wheat grown at 21 DC under a constant light intensity of 3200 f.c. were measured by infrared gas analysis twice weekly throughout the period of grain development. Measurements were made on both the intact ears and the separated grains and ear structures, in air and in a mixture of nitrogen plus 320 p.p.m. C02. Dry weights of the grains, ears, and main stems were also determined.Photosynthesis by the grains was near maximal at the light intensity measured inside the glumes, and nearly balanced the loss of C02 by dark respiration, until the grains ripened. Grain photosynthesis accounted for 33-42% of gross ear photo· synthesis. Ear photosynthesis, which was much higher in awned varieties, contributed up to 76% to total grain requirements during early growth, this proportion falling to a minimum of about 26% in Sonora (awned) and 15% in Gabo (unawned) during the period of most rapid grain growth, before rising again as grain growth slowed. Over the whole period of grain development the contribution to grain requirements by ear photosynthesis was 33% in Sonora and 20% in Gabo. The rate of photosynthesis by the flag leaf blades varied apparently in response to changes in the demand for assimilates. In Sonora, requirements by the ear during the period of most rapid grain growth were equivalent to 131 and 43 mg CO 2 per ear per day for growth and respiration of the grain respectively, while net photosynthesis at that time by the ear, flag leaf blade, and stem plus sheaths was 50, 126, and 42 mg C02 per day respectively. Photosynthesis by the ear and flag leaf blade alone could meet the needs of the ear at all times, and grain growth did not appear to be limited by the supply of assimilate.

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“…Biochemical evidence suggests that at least some TCA-cycle carbon flow is maintained in the light (e.g. Marsh et al 1965;Kanazawa et al 1970;Birch et al 1986;Elrifi and Tut-pin 1987;McCashin et al 1988), but it has been proposed that an increase in the ATP : ADP ratio during photosynthesis would result in inhibition of mitochondrial electron transport and that other processes would be responsible for NADH oxidation (Graham 1980). Stitt et al (1982) have shown, however, that light-dark transitions have little effect on cellular ATP : ADP.…”

Section: Acknowledgmentsmentioning

confidence: 99%

Respiratory losses in the light in a marine diatom: Measurements by short‐term mass spectrometry

Weger

Herzig

Falkowski

et al. 1989

Limnology & Oceanography

124

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Mass spectrometric analysis of gas exchange by the diatom Thalassiosira weisflogii grown under at the end of scotophase. When cells were poised at the DIC (dissolved inorganic carbon) compensation point in the light (DIC concentration where net photosynthesis equals zero), mitochondrial 0, consumption was only slightly higher than in the dark. Adding DIC to cells at the compensation point resulted in a rapid increase in both photosynthetic 0, evolution and mitochondrial 0, consumption, indicating that the higher mitochondrial respiration rates observed in the light are probably due to an increase in substrate supply from photosynthesis. If estimates of primary production are based on oxygen exchange, this effect is accounted for; however if radiocarbon is used to measure production, especially in short-term measurements, net production may be significantly overestimated.Phytoplankton respiration is used in aquatic ecology to quantify at least three fundamental parameters. First, knowledge of the rate of respiratory losses is required ' To whom reprint requests should be addressed.

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Effect of Light on the Tricarboxylic Acid Cycle in Scenedesmus

Cited by 64 publications

References 16 publications

Generation of Reduced Nicotinamide Adenine Dinucleotide for Nitrate Reduction in Green Leaves

Generation of Reduced Nicotinamide Adenine Dinucleotide for Nitrate Reduction in Green Leaves

Photosynthesis and Respiration by the Flag Leaf and Components of the Ear During Grain Development In Wheat

Respiratory losses in the light in a marine diatom: Measurements by short‐term mass spectrometry

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