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Why do some plants choose to absorb carbon dioxide at night? Unveiling the mystery of CAM photosynthesis!
With climate change and water shortage, the ability of plants to survive and adapt has become an important topic of modern research. In this regard, the study of Crassulacean acid metabolism (CAM) photosynthesis has gradually attracted the attention of scientists. This is a unique carbon fixation pathway that allows certain plants to absorb carbon dioxide at night and carry out photosynthesis during the day, a strategy that allows plants to efficiently use limited water resources.
Historical Background"CAM photosynthesis is an amazing adaptation that helps plants thrive in arid environments."
The discovery of CAM photosynthesis dates back to 1804, when scientist de Saussure first described the observed phenomenon in his writings. In 1812, Benjamin Heyne described the leaves of Bryophyllum in India as being acidic in the morning and tasteless in the afternoon. This observation led to further studies by physiologists, including Aubert in 1892 and Richards in 1915 on acidity and gas exchange in cacti.
How CAM works
CAM photosynthesis can be divided into two phases: night and day. At night, the plant's stomata open, allowing carbon dioxide to enter and be fixed into organic acids, a process similar to the C4 pathway. Fixed carbon dioxide is stored in the vacuole because ATP and NADPH required for photosynthesis cannot be produced at night.
"During the day, the plant's stomata close to reduce evaporation, and the stored organic acids are released and converted into carbon dioxide, which enters the Calvin cycle for photosynthesis."
Advantages of CAM
The most important advantage of CAM is that it keeps the stomata closed during most of the day. This is crucial for plants growing in dry environments because it effectively reduces water loss, allowing them to survive in extremely dry environments. Compared with plants that only carry out C3 photosynthesis, CAM carbon-fixing plants can significantly reduce water loss.
Comparison of CAM and C4 pathways
Interestingly, the CAM and C4 pathways share similarities. Both aim to improve the efficiency of RuBisCO, but in different ways: CAM is concentrated in time, while C4 is concentrated in space. In this clever way, plants can flexibly adjust the way they fix carbon according to changes in the environment.
Detailed description of the biochemical process
In the biochemical process of CAM photosynthesis, plants need to control the storage and conversion of carbon dioxide. At night, the stomata open and carbon dioxide enters the plant, reacting with phosphoenolacetone (PEP) to form oxalylacetic acid, which is then converted to malic acid for storage. During the day, plants release carbon dioxide according to their oxygen demand and introduce it into the Calvin cycle.
"CAM may be a more efficient pathway for carbon fixation for some plants, especially in water-limited environments."
How plants use CAM
Different plants use CAM to varying degrees. Some plants are "obligatory CAM plants" and can only carry out CAM photosynthesis, while others can switch modes at will according to environmental changes. This flexibility allows plants to stay alive despite changes in resources.
CAM in Aquatic and Aquatic Environments
It is noteworthy that CAM is also found in some aquatic plants. These plants usually store carbon dioxide at night because carbon dioxide diffuses much more slowly in water than in air. In the summer when environmental competition is intense, aquatic plants further strengthen this nocturnal storage mechanism and reduce respiration during photosynthesis.
Ecology and taxonomic distribution
The vast majority of CAM plants are epiphytes or succulent drought-tolerant plants, such as cacti and certain other succulents. However, CAM also occurs in some non-succulent terrestrial plants and hemi-epiphytes, such as certain trees and herbs. Surprisingly, some plants are able to switch between C3 and CAM depending on the water status of the environment, which enables them to exhibit flexible survival capabilities in the ecosystem.
Thinking about sustainable development in the future
With global climate change and the continuous changes in the ecological environment, the adaptability of CAM photosynthesis makes it a possible way for plants to survive in the future. Think about it, how does this unique photosynthesis mechanism affect our agricultural production and ecological protection?
