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

Journal Article · Thu Dec 01 00:00:00 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), Vol. 88:4; ISSN 0032-0889
• Country of Publication: United States
• Language: English

Related Subjects

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