carbon fixation occurs in the mesophyll cells in c4 plants.
carbon fixation occurs in the mesophyll cells in c4 plants.
where does carbon fixation occur in c4 plants?
in the mesophyll cells
isotopic fractionation differs between c4 carbon fixation and c3, due to the spatial separation in c4 plants of co capture (in the mesophyll cells) and the calvin cycle (in the bundle sheath cells). in c4 plants, carbon is converted to bicarbonate, fixed into oxaloacetate via the enzyme phosphoenolpyruvate (pep) carboxylase, and is then converted to malate. the malate is transported from the mesophyll to bundle sheath cells, which are impermeable to co. the internal co is concentrated in these cells as malate is reoxidized then decarboxylated back into co and pyruvate. this enables rubisco to perform catalysis while internal co is sufficiently high to avoid the competing photorespiration reaction. the delta value in the c4 pathway is -12 to -16‰ depleted in c due to the combined effects of pep carboxylase and rubisco.
fractionation of carbon isotopes in oxygenic photosynthesis
stable isotope analysis of carbon and nitrogen in human bone collagen allows bioarchaeologists to carry out dietary reconstruction and to make nutritional inferences. these chemical signatures reflect long-term dietary patterns, rather than a single meal or feast. stable isotope analysis monitors the ratio of carbon 13 to carbon 12 (c/c), which is expressed as parts per mil (per thousand) using delta notation (δc). the ratio of carbon isotopes varies according to the types of plants consumed with different photosynthesis pathways. the three photosynthesis pathways are c3 carbon fixation, c4 carbon fixation and crassulacean acid metabolism. c4 plants are mainly grasses from tropical and subtropical regions, and are adapted to higher levels of radiation than c3 plants. corn, millet and sugar cane are some well-known c4 domesticates, while all trees and shrubs use the c3 pathway. c3 plants are more common and numerous than c4 plants. both types of plants occur in tropical areas, but only c3 plants occur naturally in colder areas. c and c occur in a ratio of approximately 98.9 to 1.1.
bioarchaeology