Photorespiratory Phenomena in Maize

Volk, Richard J.; Jackson, W. A.

doi:10.1104/pp.49.2.218

Cited by 51 publications

(13 citation statements)

References 39 publications

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“…Light-dependent 02 uptake in higher plants has previously been studied in a variety of systems: isolated thylakoids (11), intact chloroplasts and cells (5,9,10,16,21), and in the intact leaf (3,6,12,22,24 80 ,um) and the filtrate was centrifuged at 350g for 3 min. The pelletted protoplasts were gently resuspended in 20 ml of the solution previously described but with 0.6 M sucrose substituted for sorbitol.…”

Section: Methodsmentioning

confidence: 99%

“…Light-dependent 02 uptake in higher plants has previously been studied in a variety of systems: isolated thylakoids (11), intact chloroplasts and cells (5,9,10,16,21), and in the intact leaf (3,6,12,22,24 Approximately 10 g of leaves were harvested for each preparation. The leaves were sliced into approximately 1-mm strips with a razor blade and digested at 30°C for 2 to 2.5 h, with illumination (1 50-w flood lamp), in 50 ml of 0.5 M sorbitol, 0.2 mM CaCI2, I mM MgC92, 0.2 mM KH2PO4, 10 mM Mes, 0.2% BSA, 2% cellulase (Onozuka S-3), and 0.2% pectinase (Macerozyme R-10) at pH 5.5 with HCI.…”

Section: Methodsmentioning

confidence: 99%

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Photoreduction of Oxygen in Mesophyll Chloroplasts of C₄ Plants

Furbank¹,

Badger²,

Osmond³

1983

Plant Physiol.

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Mesophyll chloroplasts of three C4 sub types, Panicum miliaccum (NAD-malic enzyme), Panicum maximum (PCK), and Zea mays (NADPmalic enzyme), were prepared from protoplast extracts and used to study the photoreduction of 02. The processes of 02 uptake and evolution in these preparations, which lack ribulose 1,5-bisphosphate carboxylase/ oxygenase, were studied simultaneously using stable isotopes of 02 and mass spectrometry. The responses of 02 uptake to 02 tension and addition of various substrates (3-phosphoglycerate, pyruvate, and oxaloacetate) were studied in detail. sumably dependent upon the utilization of NADPH relative to the ATP demand as has been proposed for some time (15). Few measurements have been made of chloroplast pyridine nucleotide levels (23) and manipulation of these levels in an intact system is difficult. Hence, there is little evidence of such a regulation in vivo. Although there is substantial physiological evidence for light and ATP-dependent ion transport associated with photoreduction of 02 ( 13), there is little direct evidence of the capacity of the Mehler reaction to generate ATP for photosynthetic carbon assimilation in vivo.In this study, 02 uptake and evolution in chloroplasts in mesophyll protoplast extracts from Zea mavs (NADP malic enzyme), Panicum maximum (PEP carboxykinase), and Panicum miliaceuim (NAD malic enzyme) are examined using 1802 and a mass spectrometer. The photoreduction of 02 in this system is characterized and its response to the addition ofvarious substrates is examined in order to study the regulation of the process and its ability to produce ATP. MATERIALS AND METHODSLight-dependent 02 uptake in higher plants has previously been studied in a variety of systems: isolated thylakoids (11), intact chloroplasts and cells (5,9,10,16,21), and in the intact leaf (3,6,12,22,24 Approximately 10 g of leaves were harvested for each preparation. The leaves were sliced into approximately 1-mm strips with a razor blade and digested at 30°C for 2 to 2.5 h, with illumination (1 50-w flood lamp), in 50 ml of 0.5 M sorbitol, 0.2 mM CaCI2, I mM MgC92, 0.2 mM KH2PO4, 10 mM Mes, 0.2% BSA, 2% cellulase (Onozuka S-3), and 0.2% pectinase (Macerozyme R-10) at pH 5.5 with HCI. Leafstrips were examined under a microscope each hour to determine the correct digestion time. When gentle agitation of the tissue resulted in mesophyll protoplast release, the incubation medium was carefully decanted and the leaf strips washed in a plastic tea strainer with 50 ml of 0.6 M sorbitol, 5 mM Hepes, 1 mM MgCl2, 0.2 mM CaCl2, 0.2 mM KH2PO4, and 0.1 % BSA, pH 7.8. The filtrate was passed through two nylon nets (250 ,um net and then an 80 ,um) and the filtrate was centrifuged at 350g for 3 min. The pelletted protoplasts were gently resuspended in 20 ml of the solution previously described but with 0.6 M sucrose substituted for sorbitol. The suspension 1038 www.plantphysiol.org on May 12, 2018 -Published by Downloaded from

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“…Light-dependent 02 uptake in higher plants has previously been studied in a variety of systems: isolated thylakoids (11), intact chloroplasts and cells (5,9,10,16,21), and in the intact leaf (3,6,12,22,24 80 ,um) and the filtrate was centrifuged at 350g for 3 min. The pelletted protoplasts were gently resuspended in 20 ml of the solution previously described but with 0.6 M sucrose substituted for sorbitol.…”

Section: Methodsmentioning

confidence: 99%

“…Light-dependent 02 uptake in higher plants has previously been studied in a variety of systems: isolated thylakoids (11), intact chloroplasts and cells (5,9,10,16,21), and in the intact leaf (3,6,12,22,24 Approximately 10 g of leaves were harvested for each preparation. The leaves were sliced into approximately 1-mm strips with a razor blade and digested at 30°C for 2 to 2.5 h, with illumination (1 50-w flood lamp), in 50 ml of 0.5 M sorbitol, 0.2 mM CaCI2, I mM MgC92, 0.2 mM KH2PO4, 10 mM Mes, 0.2% BSA, 2% cellulase (Onozuka S-3), and 0.2% pectinase (Macerozyme R-10) at pH 5.5 with HCI.…”

Section: Methodsmentioning

confidence: 99%

Photoreduction of Oxygen in Mesophyll Chloroplasts of C₄ Plants

Furbank¹,

Badger²,

Osmond³

1983

Plant Physiol.

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“…The photorespiratory rate in C4 plants is unknown. It is assumed to be low, since these plants exhibit little or no light-dependent, oxygen-sensitive CO2 evolution (6,10,34).…”

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confidence: 99%

Photorespiratory Rates in Wheat and Maize as Determined by ¹⁸O-Labeling

Veau¹,

Burris²

1989

Plant Physiol.

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A method was devised to quantify short-term photorespiratory rates in terrestrial plants using 180-intermediates of the glycolate pathway, specifically glycolate, glycine, and serine. The pathway intermediates were isolated and analyzed on a GC/MS to determine molecular percent 180-enrichment. Rates of glycolate synthesis were determined from '10-labeling kinetics of the intermediates, derived rate equations, and nonlinear regression techniques. Glycolate synthesis in wheat (Triticum aestivum L.), a C3 plant, and maize (Zea mays L.), a C4 plant, was stimulated by high 02 concentrations and inhibited by high CO2 concentrations. The synthesis rates were 7.3, 2.1, and 0.7 micromoles per square decimeter per minute under a 21% 02 and 0.035% Co2 atmosphere for leaf tissue of wheat, maize seedlings, and 3-month-old maize, respectively. Photorespiratory CO2 evolution rates were estimated to be 27, 6, and 2%, respectively, of net photosynthesis for the three groups of plants under the above atmosphere. The results from maize tissue support the hypothesis that C4 plants photorespire, albeit at a reduced rate in comparison to C3 plants, and that the C02/02 ratio in the bundle sheath of maize is higher in mature tissue than in seedling tissue. The pool size of the three photorespiratory intermediates remained constant and were unaffected by changes in either CO2 or 02 concentrations throughout the 10-minute labeling period. This suggests that photorespiratory metabolism is regulated by other mechanism besides phosphoglycolate synthesis by ribulose-1,5-bisphosphate carboxylase/oxygenase, at least under short-term conditions. Other mechanisms could be altemate modes of synthesis of the intermediates, regulation of some of the enzymes of the photorespiratory pathway, or regulation of carbon flow between organelles involved in photorespiration. The glycolate pool became nearly 100% 10-labeled under an atmosphere of 40% 02. This pool failed to become 100% 180-enriched under lower 02 concentrations.

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“…In leaves of higher plants, this conclusion is supported by studies with labeled tricarboxylic acid cycle intermediates (6,7), and by the persistence in the light of 02 uptake at low concentrations of 0°known to inhibit glycolate synthesis and metabolism, or photorespiration (25,30). The role of continued tricarboxylic acid cycle respiration in the light in green cells is not clearly understood but it contributes to C02-generating reactions in these tissues (23,30). In leaves of some C4 plants.…”

mentioning

confidence: 66%