carbon fixation is the most common of three metabolic pathways for carbon fixation in photosynthesis, along with C4 carbon fixation| and CAM. This process converts carbon dioxide and ribulose bisphosphate into two molecules of 3-phosphoglycerate through the following reaction: This reaction occurs in all plants as the first step of the Calvin–Benson cycle. '' leaf. Vascular bundles shown. Drawing based on microscopic images courtesy of Cambridge UniversityPlant Sciences Department. Plants that survive solely on fixation tend to thrive in areas where sunlight intensity is moderate, temperatures are moderate, carbon dioxide concentrations are around 200 ppm or higher, and groundwater is plentiful. The plants, originating during Mesozoic and Paleozoic eras, predate the C4 carbon fixation| plants and still represent approximately 95% of Earth's plant biomass, including important food crops such as rice, wheat, soybeans and barley. plants cannot grow in very hot areas because RuBisCO incorporates more oxygen into RuBP as temperatures increase. This leads to photorespiration, which leads to a net loss of carbon and nitrogen from the plant and can therefore limit growth. plants lose up to 97% of the water taken up through their roots to transpiration. In dry areas, plants shut their stomata to reduce water loss, but this stops from entering the leaves and therefore reduces the concentration of in the leaves. This lowers the :O2 ratio and therefore also increases photorespiration. and CAM plants have adaptations that allow them to survive in hot and dry areas, and they can therefore out-compete plants in these areas. The isotopic signature of plants shows higher degree of 13C depletion than the plants, due to variation in fractionation of carbon isotopes in oxygenic photosynthesis across plant types. Scientists have designed new metabolism pathways which reduces the losses to photorespiration, by more efficiently metabolizing the toxicglycolate produced. This resulted in over 40% increase in biomass production in their model organism in their test conditions. The scientists are optimistic that this optimization can also be implemented in other crops like wheat.
