Use of isotopes to explore the physiology and biochemistry of photorespiration and its effects on crop yields

Conference · Wed Jan 01 04:00:00 EST 1975

OSTI ID:4013816

Keys, A J; Bird, I F; Cornelius, M J; Kumarasinghe, S; Whittingham, C P

Crop yield depends on the rates of photosynthesis, transport of assimilate, growth of useful parts of the plant, photorespiration and dark respiration. Photorespiration is closely associated with photosynthesis; it probably has a direct effect on photosynthetic efficiency and causes a loss of recently assimilated carbon as CO$sub 2$. Photorespiration is, however, associated with phosphorylation of ADP to ATP in mitochondria and results in transport of carbon out of the chloroplast. Serine, a major product of photorespiration, is readily converted to sucrose in leaves. Using [$sup 14$C] serine it was shown that sucrose synthesis from serine required concurrent photosynthetic assimilation of CO$sub 2$ and aerobic conditions. This suggests sucrose synthesis from serine may be dependent upon continuing photorespiration for energy and may not directly involve metabolism in the chloroplast. In wheat leaves, much if not all the carbon assimilated in air may be metabolized by the photorespiratory pathway (glycollate pathway). This was shown by rates of change of $sup 14$C in intermediates when conditions were changed suddenly from steady photosynthesis in the presence of $sup 14$CO$sub 2$. On the other hand, intramolecular labelling of sucrose, following short periods of photosynthesis in $sup 14$CO$sub 2$, was not entirely consistent with all sucrose being made from intermediates of the glycollate pathway, even in air containing 150 v. p. m. $sup 14$CO$sub 2$. (auth)

• Research Organization: Rothamsted Experimental Station, Harpenden, Eng.
• NSA Number: NSA-33-026377
• OSTI ID: 4013816
• Country of Publication: IAEA
• Language: English

Related Subjects

*ADP-- BIOCHEMICAL REACTION KINETICS
*ATP-- BIOCHEMICAL REACTION KINETICS
*CARBOHYDRATES-- BIOCHEMICAL REACTION KINETICS
*MAIZE-- RESPIRATION
*MITOCHONDRIA-- BIOCHEMICAL REACTION KINETICS
*WHEAT-- RESPIRATION
551201*
AGRICULTURE
CARBON 14
CARBON DIOXIDE
N48810* --Life Sciences--New Tracer Techniques--Animal Husbandry
N48830 --Life Sciences--New Tracer Techniques--Other
PHOSPHORYLATION
PHYSIOLOGY
PLANTS
TRACER TECHNIQUES