Pathways of Carbon Fixation in Green Plants

An Early Arabidopsis Demonstration. Resolving a Few Issues Concerning Photorespiration

“…1; 23,24). It had also been established that the CO 2 released from glycolate metabolism was the source of at least some of the CO 2 released during a process that had become known as photorespiration (4,25). However, there was no generally accepted explanation for the biosynthetic origin of glycolate or why it was rapidly labeled by 14 CO 2 .…”

“…I have never witnessed any public arguments comparable with those that dominated the 1978 Gordon Conference on photosynthesis. The opposition was led by Israel Zelitch who was of the opinion that the RuBP oxygenase-based mechanism of glycolate synthesis was inconsistent with many miscellaneous observations that had been made during the long search for the source of photorespiratory glycolate (25). Zelitch and others also argued that phosphoglycolate could not be an important precursor of photorespiratory glycolate because measurements of flux through phosphoglycolate were much too low to account for the magnitude of photorespiratory CO 2 metabolism (25).…”

“…One need only compare the views expressed in two contemporaneous reviews of the subject to get a clear impression of a major scientific controversy of the period (4,25). The problem seemed important because, although there was a lot of disagreement about the mechanism of photorespiration, there was broad agreement that if it could be genetically reduced it would lead to a major increase in primary plant productivity.…”

Photorespiration in C3 and C4 Plant Tissue Cultures

“…It has been estimated that in C3 plants, the process of photorespiration oxidizes up to 50% of the newly synthesized photosynthetic products, whereas in C4 plants, photorespiration is either not present or occurs in much reduced amounts (20). In addition to the lack of apparent photorespiration and significantly greater net assimilation rate, C4 plants also possess several other structural and physiological features which distinguish them from C3 plants.…”

Effects of Glycolate Pathway Intermediates on Glycine Decarboxylation and Serine Synthesis in Pea (Pisum sativum L.)

“…The metabolism of glycolate in photosynthetic organisms is an important biochemical process because the CO2 evolution resulting from the oxidation of the carboxyl carbon group of a glycolate pathway intermediate is thought to account for photorespiratory CO2 production (30) and NH3 recycling (15). There is still controversy regarding the immediate precursor of the photorespired CO2.…”