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Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions [1] that allows a plant to photosynthesize during the day, but only exchange gases at night. In a plant using full CAM, the stomata in the leaves remain shut during the day to reduce ...
At night, plants respire, and gas exchange partly reverses: water vapor is still lost (but to a smaller extent), but oxygen is now taken up and carbon dioxide released. [36] Fig. 11. A stylised cross-section of a euphyllophyte plant leaf, showing the key plant organs involved in gas exchange. Plant gas exchange occurs mostly through the leaves.
CAM plants, such as cacti and succulent plants, also use the enzyme PEP carboxylase to capture carbon dioxide, but only at night. Crassulacean acid metabolism allows plants to conduct most of their gas exchange in the cooler night-time air, sequestering carbon in 4-carbon sugars which can be released to the photosynthesizing cells during the day.
Photosynthesis, plant water transport and gas exchange are regulated by stomatal function which is important in the functioning of plants. [30] Stomata are responsive to light with blue light being almost 10 times as effective as red light in causing stomatal response.
SV channels have been shown to function as cation channels that are permeable to Ca 2+ ions, [35] but their exact functions are not yet known in plants. [39] Guard cells control gas exchange and ion exchange through opening and closing. K+ is one ion that flows both into and out of the cell, causing a positive charge to develop.
In plant bodies that produce secondary growth, lenticels promote gas exchange of oxygen, carbon dioxide, and water vapor. [8] Lenticel formation usually begins beneath stomatal complexes during primary growth preceding the development of the first periderm.
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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 ...