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The δ 13 C of C3 plants depends on the relationship between stomatal conductance and photosynthetic rate, which is a good proxy of water use efficiency in the leaf. [19] C3 plants with high water-use efficiency tend to be less fractionated in 13 C (i.e., δ 13 C is relatively less negative) compared to C3 plants with low water-use efficiency. [19]
About 8,100 plant species use C 4 carbon fixation, which represents about 3% of all terrestrial species of plants. [ 27 ] [ 28 ] All these 8,100 species are angiosperms . C 4 carbon fixation is more common in monocots compared with dicots , with 40% of monocots using the C 4 pathway [ clarification needed ] , compared with only 4.5% of dicots.
C 3 carbon fixation occurs in all plants as the first step of the Calvin–Benson cycle. (In C 4 and CAM plants, carbon dioxide is drawn out of malate and into this reaction rather than directly from the air.) Cross section of a C 3 plant, specifically of an Arabidopsis thaliana leaf. Vascular bundles shown.
The simpler C3 cycle which operates in most plants is adapted to wetter darker environments, such as many northern latitudes. [citation needed] Maize, sugar cane, and sorghum are C4 plants. These plants are economically important in part because of their relatively high photosynthetic efficiencies compared to many other crops. Pineapple is a ...
Maize (Zea mays, Poaceae) is the most widely cultivated C 4 plant.[1]In botany, C 4 carbon fixation is one of three known methods of photosynthesis used by plants. C 4 plants increase their photosynthetic efficiency by reducing or suppressing photorespiration, which mainly occurs under low atmospheric CO 2 concentration, high light, high temperature, drought, and salinity.
In addition, there are two types of plants with different biochemical pathways; the C3 carbon fixation, where the isotope separation effect is more pronounced, C4 carbon fixation, where the heavier 13 C is less depleted, and Crassulacean Acid Metabolism (CAM) plants, where the effect is similar but less pronounced than with C 4 plants.
Changes in atmospheric CO 2 concentrations also influence δ 13 C, with lower pCO 2 during glacial periods causing isotopic discrimination in plants using dissolved CO 2. Changes in Dominant Vegetation Within the Watershed: Shifts in watershed vegetation, especially transitions between C3 and C4 photosynthetic pathways, significantly alter the ...
The CO 2 compensation point (Γ) is the CO 2 concentration at which the rate of photosynthesis exactly matches the rate of respiration. There is a significant difference in Γ between C 3 plants and C 4 plants: on land, the typical value for Γ in a C 3 plant ranges from 40–100 μmol/mol, while in C 4 plants the values are lower at 3–10 μmol/mol. Plants with a weaker CCM, such as C2 ...