Steady-state photosynthesis in alfalfa leaflets

Journal Article · Mon Aug 01 04:00:00 EDT 1977 · Plant Physiol.; (United States)

OSTI ID:5113617

Platt, S G; Plaut, Z; Bassham, J A

When the CO/sub 2/ concentration to which Medicago sativa L. var. El Unico leaflets were exposed was increased from half-saturation to saturation (doubled rate of photosynthesis), glycolate and glycine production apparently decreased due to inhibition of a portion of the glycolate pathway. Serine and glycerte production was not inhibited. We conclude that serine and glycerate were made from 3-phosphoglycerate and not from glycolate and that the conversion of glycine to serine may not be the major source of photorespiratory CO/sub 2/ in alfalfa. In investigations of glycolate and photorespiratory metabolism, separate labeling data should be obtained for glycine and serine as those two amino acids may be produced from different precursors and respond differently to environmental perturbations. The increased photosynthetic rate (at saturating CO/sub 2/) resulted in greater labeling of both soluble and insoluble products. Sucrose labeling increased sharply, but there was no major shift of tracer carbon flow into sucrose relative to other metabolites. The flow of carbon from the reductive pentose phosphate cycle into the production of tricarboxylic acid cycle intermediates and amino acids increased. Only small absolute increases occurred in steady-state pool sizes of metabolites of the reductive pentose phosphate cycle at elevated CO/sub 2/, providing further evidence that the cycle is well regulated.

• Research Organization: Lawrence Berkeley Lab., CA
• OSTI ID: 5113617
• Journal Information: Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 60:2; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

550500* -- Metabolism
59 BASIC BIOLOGICAL SCIENCES
ALFALFA
AMINO ACIDS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BIOMASS
CARBOHYDRATES
CARBON 14
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON ISOTOPES
CARBON OXIDES
CARBOXYLIC ACIDS
CHALCOGENIDES
CHEMICAL REACTIONS
DISACCHARIDES
ECOLOGICAL CONCENTRATION
ENERGY SOURCES
EVEN-EVEN NUCLEI
GLYCINE
HYDROXY ACIDS
INHIBITION
ISOTOPES
LEAVES
LEGUMINOSAE
LIGHT NUCLEI
METABOLISM
NUCLEI
OLIGOSACCHARIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PLANTS
RADIOISOTOPES
RENEWABLE ENERGY SOURCES
RESPIRATION
SACCHARIDES
SACCHAROSE
SERINE
SYNTHESIS
YEARS LIVING RADIOISOTOPES