Effects of carbon dioxide and oxygen on the regulation of photosynthetic carbon metabolism by ammonia in spinach mesophyll cells

Journal Article · Thu Jan 01 00:00:00 EST 1981 · Plant Physiol.; (United States)

DOI:https://doi.org/10.1104/pp.68.6.1231· OSTI ID:5300619

Lawyer, A L; Cornwell, K L; Larsen, P O; Bassham, J A

Photosynthetic carbon metabolism of isolated spinach mesophyll cells was characterized under conditions favoring photorespiratory (PR; 0.04% CO/sub 2/ and 20% O/sub 2/) and nonphotorespiratory (NPR; 0.2% CO/sub 2/ and 2% O/sub 2/) metabolism, as well as intermediate conditions. Comparisons were made between the metabolic effects of extracellularly supplied NH/sub 4//sup +/ and intracellular NH/sub 4//sup +/, produced primarily via PR metabolism. The metabolic effects of /sup 14/CO/sub 2/ fixation under PR conditions were similar to perturbations of photosynthetic metabolism brought about by externally supplied NH/sub 4//sup +/; both increased labeling and intracellular concentrations of glutamine at the expense of glutamate and increased anaplerotic synthesis through ..cap alpha..-ketoglutarate. The metabolic effects of added NH/sub 4//sup +/ during NPR fixation were greater than those during PR fixation, presumably due to lower initial NH/sub 4//sup +/ levels during NPR fixation. During PR fixation, addition of ammonia caused decreased pools and labeling of glutamate and serine and increased glycolate, glyoxylate, and glycine labeling. The glycolate pathway was thus affected by increased rates of carbon flow and decreased glutamate availability for glyoxylate transamination, resulting in increased usage of serine for transamination. Sucrose labeling decreased with NH/sub 4//sup +/ addition only during PR fixation, suggesting that higher photosynthetic rates under NPR conditions can accommodate the increased drain of carbon toward amino acid synthesis while maintaining sucrose synthesis.

• Research Organization: Lawrence Berkeley Lab., CA
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5300619
• Journal Information: Plant Physiol.; (United States), Vol. 68
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
AMMONIA
BIOLOGICAL EFFECTS
CARBON
METABOLISM
PHOTOSYNTHESIS
BIOLOGICAL MODELS
AMINO ACIDS
CARBON 14 COMPOUNDS
CARBON CYCLE
CARBON DIOXIDE
CARBON DIOXIDE FIXATION
OXYGEN
PLANT CELLS
SPINACH
CARBON COMPOUNDS
CARBON OXIDES
CARBOXYLIC ACIDS
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
FOOD
HYDRIDES
HYDROGEN COMPOUNDS
LABELLED COMPOUNDS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
SYNTHESIS
VEGETABLES
550501* - Metabolism- Tracer Techniques
551001 - Physiological Systems- Tracer Techniques