Spinach leaf chloroplast CO sub 2 and NO sub 2 sup minus photoassimilations do not compete for photogenerated reductant

Journal Article · Thu Dec 01 04:00:00 EST 1988 · Plant Physiology; (USA)

DOI:https://doi.org/10.1104/pp.88.4.1373· OSTI ID:6999244

Robinson, J M ^[1]

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1. Dept. of Agriculture, Beltsville, MD (USA)

Potential competition between CO{sub 2} and NO{sub 2}{sup {minus}} photoassimilation for photogenerated reductant (e.g. reduced ferredoxin and NADPH) was examined employing isolates of mesophyll cells and intact chloroplasts derived from mature source spinach leaves. Variations in the magnitude of incident light energy were used to manipulate the supply of reductant in situ within chloroplasts. Leaf cell and plastid isolates were fed with saturating CO{sub 2} and/or NO{sub 2}{sup {minus}} to produce the highest demand for reductant by CO{sub 2} and/or NO{sub 2}{sup {minus}} assimilatory processes (enzymes). Even in the presence of CO{sub 2} fixation, NO{sub 2}{sup {minus}} reduction in intact leaf cell isolates as well as plastid isolates was maximal at light energies as low as 50 to 200 microeinsteins per second per square meter. Simultaneously, 500 to 800 microeinsteins per second per square meter were required to support maximal CO{sub 2} assimilation. Regardless of the magnitude of the incident light energy, CO{sub 2} assimilation did not repress NO{sub 2}{sup {minus}} reduction, nor were these two processes mutually repressed. These observations have been interpreted to mean that reduced ferredoxin levels in situ in the plastids of mature source leaf mesophyll cells were adequate to supply the concurrent maximal demands exerted by enzymes associated with CO{sub 2} as well as with inorganic nitrogen photoassimilation.

• OSTI ID: 6999244
• Journal Information: Plant Physiology; (USA), Journal Name: Plant Physiology; (USA) Vol. 88:4; ISSN 0032-0889; ISSN PLPHA
• Country of Publication: United States
• Language: English

Related Subjects

550500* -- Metabolism
59 BASIC BIOLOGICAL SCIENCES
BIOCHEMICAL REACTION KINETICS
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CELL CONSTITUENTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHLOROPLASTS
COENZYMES
FERREDOXIN
FOOD
KINETICS
LEAVES
MAGNOLIOPHYTA
MAGNOLIOPSIDA
METALLOPROTEINS
NADP
NITROGEN COMPOUNDS
NITROGEN DIOXIDE
NITROGEN OXIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PHOTOSYNTHESIS
PLANT CELLS
PLANTS
PROTEINS
REACTION KINETICS
SPINACH
SYNTHESIS
VEGETABLES