The Crassulacean acid metabolism is among the most unique photosynthetic pathways. It is a characteristic very unique and common among several specially adapted plants which gives excellent performance in dry and semi-arid habitats. Such a pathway confers to the plants' wonderful means through which they can afford and effectively capture and utilise carbon dioxide and still be in a position to conserve water efficiently, hence making them very good at surviving in dry environments. Carbon fixation takes place in CAM plants in a manner quite different from either C3 or C4 plants.
Although all photosynthetic plants photosynthesize, CAMs go a step further and carry out a very strange photosynthetic activity by which they fix carbon dioxide at night rather than during the day. These adaptations greatly avoid the loss of water due to transpiration, especially in conditions when the atmosphere is hot and dry. The major steps are:
In plants with CAM, the stoma opens at night when it becomes cold and humid. Carbon dioxide will gain entry then through the opened stomata. This carbon dioxide is fixed into a 4-carbon compound, normally malate, which is then stored in vacuoles.The malate is thus stored in the vacuoles, and it is to be used at night. Thus, carbon dioxide is saved in a form that can be used both day and night.
During the day, after stomata have been closed to prevent the loss of water, the stored malate is again re-converted for use as carbon dioxide. This CO2 results in the production of sugar during the Calvin cycle.
Some Of These Features Of The Cam Plants That All Add To Survival In Adverse Conditions are those such as stomatal behaviour, in that the stomata are closed during the day and hence no water is lost, and they only open up at night to take in carbon dioxide. Water use efficiency is attained due to carbon dioxide fixing at night, hence reduced transpiration, and less water loss, which makes the plants thus perform better even in arid conditions.
Most CAM plants are succulent—for instance, cacti and some orchids—a characteristic that enables them to store water in their tissue to survive for a long time without water.
There are so many plants that are examples of CAM, but some common ones are stated below:
Cacti:
The symbolic plants since they can survive in the most dried environment, they fix CO2 through photosynthesis they carry with the use of CAM.
Pineapple:
The tropical fruit uses CAM photosynthesis to survive in environments that are warm and humid-tensed, and therefore conserved water.
Orchids:
Most orchids have their niches in variable water availability conditions. CAM affords them an advantage in maximizing their efficiency for carbon fixation.
The following are some of the benefits that are imparted to plants, which live in dry environments, by the CAM pathway:
CAM plants can reduce the loss of water to a considerable degree during night carbon fixation, and hence survive in conditions where water is at a minimum.
This ability to store carbon dioxide as malate gives CAM plants the ability to fix a lot of carbon during the day even when the stomata becomes closed.
This may therefore make it possible for CAM plants in any other case uninhabitable to thrive, and this will increase the biodiversity in the arid ecosystems.
The CAM plants open their stomata at night when there are low temperatures and high humidity levels. This prevents the loss of water by taking up carbon dioxide.
Typical examples of CAM plants include the cacti, pineapple, and several orchids.
CAM photosynthesis saves enough amounts of water and allows efficient fixation of CO2, thus, it enables survival during drought conditions.
At 4 carbons, malate sequesters carbon dioxide at night and gives it back during the day to be reconstituted into carbon dioxide, therefore reloading the Calvin cycle with CO2.
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