C4 photosynthesis in the context of "C3 carbon fixation"

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⭐ Core Definition: C4 photosynthesis

C4 carbon fixation or the Hatch–Slack pathway is one of three known photosynthetic processes of carbon fixation in plants. It owes the names to the 1960s discovery by Marshall Davidson Hatch and Charles Roger Slack.

C4 fixation is an addition to the ancestral and more common C3 carbon fixation. The main carboxylating enzyme in C3 photosynthesis is called RuBisCO, which catalyses two distinct reactions using either CO2 (carboxylation) or oxygen (oxygenation) as a substrate. RuBisCO oxygenation gives rise to phosphoglycolate, which is toxic and requires the expenditure of energy to recycle through photorespiration. C4 photosynthesis reduces photorespiration by concentrating CO2 around RuBisCO.

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C4 photosynthesis in the context of Polyphyly

A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as homoplasies, which are explained as a result of convergent evolution. The arrangement of the members of a polyphyletic group is called a polyphyly /ˈpɒlɪˌfli/. It is contrasted with monophyly and paraphyly.

For example, the biological characteristic of warm-bloodedness evolved separately in the ancestors of mammals and the ancestors of birds; "warm-blooded animals" is therefore a polyphyletic grouping. Other examples of polyphyletic groups are algae, C4 photosynthetic plants, and edentates.

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C4 photosynthesis in the context of Proso millet

Panicum miliaceum is a grain crop with many common names, including proso millet, broomcorn millet, common millet, hog millet, Kashfi millet, red millet, and white millet. Archaeobotanical evidence suggests millet was first domesticated about 10,000 BP in Northern China. Major cultivated areas include Northern China, Himachal Pradesh of India, Nepal, Russia, Ukraine, Belarus, the Middle East, Turkey, Romania, and the Great Plains states of the United States. About 500,000 acres (200,000 hectares) are grown each year. The crop is notable both for its extremely short lifecycle, with some varieties producing grain only 60 days after planting, and its low water requirements, producing grain more efficiently per unit of moisture than any other grain species tested. The name "proso millet" comes from the pan-Slavic general and generic name for millet (Serbo-Croatian: proso/просо, Czech: proso, Polish: proso, Russian: просо).

Proso millet is a relative of foxtail millet, pearl millet, maize, and sorghum within the grass subfamily Panicoideae. While all of these crops use C4 photosynthesis, the others all employ the NADP-ME as their primary carbon shuttle pathway, while the primary C4 carbon shuttle in proso millet is the NAD-ME pathway.

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