Home / 英国北安普顿生理学ASSIGNMENT代写:卡尔文循环

CAM植物与“常规”植物(称为C3植物)的不同之处在于它们的光合作用。在正常的光合作用中,当二氧化碳(CO2),水(H2O),光和称为Rubisco的酶共同产生氧气,水和两个含有三个碳的碳分子(因此,名称C3)时,形成葡萄糖。这实际上是一个效率低下的过程,原因有两个:大气中的碳含量低,以及Rubisco对二氧化碳的亲和力低。因此,植物必须产生高水平的Rubisco才能“抓住”尽可能多的二氧化碳。氧气(O2)也会影响这个过程,因为任何未使用的Rubisco都会被O2氧化。植物中的氧气含量越高,Rubisco就越少;因此,较少的碳被同化并制成葡萄糖。 C3植物通过在白天保持其气孔开放来处理这种情况,以便尽可能多地收集碳,即使它们在此过程中会损失大量的水(通过蒸腾作用)。沙漠中的植物在白天不能让它们的气孔开放,因为它们会失去太多宝贵的水。干旱环境中的植物必须能够保持所有的水!因此,它必须以不同的方式处理光合作用。 CAM植物需要在夜间打开气孔,此时通过蒸腾减少水分流失的可能性。该工厂仍然可以在晚上吸收二氧化碳。早上,苹果酸是由二氧化碳形成的(还记得海恩提到的苦味吗?),白天在封闭的气孔条件下,酸被脱羧(分解)成二氧化碳。然后通过卡尔文循环将CO2制成必需的碳水化合物。


CAM plants differ from “conventional” plants (called C3 plants) in their photosynthesis. In normal photosynthesis, when carbon dioxide (CO2), water (H2O), light and an enzyme called Rubisco produce oxygen together, water and two carbon molecules containing three carbons (hence, the name C3), glucose is formed. . This is actually an inefficient process for two reasons: the low carbon content in the atmosphere and the low affinity of Rubisco for carbon dioxide. Therefore, plants must produce high levels of Rubisco in order to “catch” as much carbon dioxide as possible. Oxygen (O2) also affects this process because any unused Rubisco will be oxidized by O2. The higher the oxygen content in the plant, the less Rubisco is; therefore, less carbon is assimilated and made into glucose. C3 plants treat this by keeping their stomata open during the day to collect as much carbon as possible, even if they lose a lot of water (by transpiration) during this process. Plants in the desert cannot keep their stomata open during the day because they lose too much precious water. Plants in arid environments must be able to keep all the water! Therefore, it must handle photosynthesis in different ways. CAM plants need to open the stomata at night, at which point the possibility of water loss is reduced by transpiration. The plant can still absorb carbon dioxide at night. In the morning, malic acid is formed by carbon dioxide (remember the bitter taste mentioned by Haien?). During the daytime, under closed pore conditions, the acid is decarboxylated (decomposed) into carbon dioxide. The CO2 is then made into the necessary carbohydrates through the Calvin cycle.