Question

c4 plants formation in

Answer 1

By the end of the 1950s it was widely believed that all plants used the same pathway of photosynthesis. This pathway was called the Calvin cycle or photosynthetic carbon reduction (PCR) cycle and began with the incorporation of carbon dioxide (CO2) into the 5-carbon sugar ribulose bisphosphate (RuBP) to form a six-carbon intermediate which immediately splits to form two C3 molecules of 3-phosphoglycerate. In the latter half of the next decade Marshall Hatch and Roger Slack with, PhD students Hilary Johnson and John Andrews, working at the Brisbane laboratory of the Colonial Sugar Refining Co Ltd., provided evidence for the mechanism, enzymology and regulation of an alternative photosynthetic process operating in leaves of sugarcane. In this process, the first products of CO2 fixation are the C4 dicarboxylic acids, malate, aspartate and oxaloacetate, not the C3 molecule 3-phosphoglycerate. They named the process the C4 dicarboxylic pathway of photosynthesis, abbreviated later to the C4pathway or C4 photosynthesis. Several other grass species and some species from other families were shown to have a similar mechanism. This alternative process, the NADP-malic enzyme-type, is one of three types of C4photosynthesis subsequently identified in later years.