CAM Plants

CAM plants are those that absorb CO₂ through the Crassulacean acid metabolism or CAM process. It was initially found in plants belonging to the Crassulaceae family. They can be found in areas that are barren and arid. The CAM pathway has been modified to reduce photorespiration and moisture loss. Cactus, pineapple, and other plants are examples of CAM plants.

CAM Plants

Crassulacean Acid Metabolism, is a kind of carbon fixation that certain plants developed in arid environments.

The stomata, resemble tiny mouths and are located everywhere on the surface of leaves throughout many plants, opening throughout the day to absorb CO₂ and discharge O₂. Because they utilize it as a reservoir for carbon atoms in sugars, proteins, nucleotides, and other essential components of life, plants are required to take in CO₂. The waste O₂ that remains after the carbon from CO₂ has been absorbed into sugar should be released.

Since energy from the Sun is obtained during the day, numerous plants activate the stomata throughout that time. The chloroplasts capture solar energy and utilize it to produce ATP and NADPH. The fixation of carbon, becoming sugar, is then driven by these molecules that store short-term energy. On the other hand, whereas if stomata are open during the warm, dry seasons in plants that live in extremely arid settings, hazardous quantities of water can sometimes be drained. The amount of water lost by opening the stomata during the night, when it’s often much cooler in dry conditions, is significantly lower.

CAM plants absorb CO₂ at nighttime and retain it as malate, a four-carbon acid, to fulfill they have to integrate the Sun’s energy using CO₂ from the air. Later, throughout the day, the malate is released so that it can combine with the ATP and NADPH produced by the Sun’s energy. Shutting their stomata during hotter parts of the day enables the plants to preserve water.

Evolution of CAM Plants

The RuBP carboxylase, often known as Rubisco, is the enzyme that catalyzes the reaction between RuBP and CO₂. Rubisco is said to be the protein that is most prevalent around the globe. However, Rubisco has a severe issue and is less effective in grabbing Carbon 2. Rubisco begins collecting oxygen when the level of CO₂ in the air within the leaf drops too low. The end outcome of this procedure, known as photorespiration, is that glucose is burnt off rather than produced. In hot, dry weather, when they should maintain their attempt to trick (leaf pores) covered to prevent dehydration, plants experience greater photorespiration problems.

Different methods have developed over time among various plant groupings to deal with the issue of photorespiration. These plants, also known as C4 plants but also CAM plants, use a significantly more effective enzyme to bind carbon dioxide at first. This enables a more effective CO₂ harvest, enabling the plants to store enough CO₂ despite frequently activating their stomates. The Calvin-Benson cycle is how each consumes CO₂ after that.

The enzyme PEP carboxylase is used by C4 (“four-carbon”) plants to initially link CO₂ to PEP (phosphoenolpyruvate) to create the four-carbon compound OAA (oxaloacetate). This occurs in mesophyll cells, which are a type of loosely packed cell. The bundle sheath cells, which encircle the leaf vein, are subsequently pumped with OAA. There, CO₂ is released for usage by Rubisco. C4 plants promote the effective operation of the Calvin-Benson cycle and reduce photorespiration by accumulating Carbon dioxide (CO₂)in the bundle sheath cells. Maize, sugar beets, and numerous other tropical grasslands are C4 plants.

In the beginning, CAM (plants also bind CO₂ to PEP to create OAA. However, CAM plants absorb carbon during the night and then retain the OAA inside huge vacuoles inside the cell, as opposed to storing carbon throughout the day and pumping the OAA to neighboring cells. This enables them to utilize the CO₂ again for the Calvin-Benson cycle throughout the day, when it may be powered by the sun’s energy, but to have the stomates released in the chill of the evening, preventing water loss. Cacti and numerous other succulent plants are examples of CAM plants, which are more prevalent than C4 plants.

CAM Photosynthesis

Plants that use this route are referred to as C4 plants since they are effectively able to fix Carbon dioxide at low concentrations. These plants convert CO₂ first into oxaloacetate, a C4 chemical This takes place in cells known as mesophyll cells. To create the four-carbon complex oxaloacetate, Carbon dioxide would be first bonded to the three-carbon compound PEP. The phosphoenol pyruvate carboxylase enzyme, which catalyzes this process, stores Carbon dioxide very effectively, reducing the amount of stomatal opening required by C4 plants.

The C4 Route C4 plants are those that utilize the C4 pathway, which is built to effectively absorb Carbon dioxide at small concentrations. These plants convert CO₂ into oxaloacetate, a C4 molecule with four carbons. This takes place in cells known as mesophyll cells. To create the four-carbon complex oxaloacetate, CO₂ is bonded to the three-carbon compound pep. The PEP carboxylase enzyme, which catalyzes this process, fixes CO₂ very effectively, reducing the amount of stomatal opening required by C4 plants. The percentage inhibition of NADPH is subsequently used to transform the oxaloacetate into malate, a different four-carbon molecule. The malate subsequently leaves the mesophyll cells & reaches the bundle sheathing cells’ chloroplasts, which are specialized cells.

Here, the four-carbon chemical malate is catabolized to yield CO₂, pyruvate, a three-carbon product, and NADPH. When CO₂ and rubisco bisphosphate mix, the  Calvin cycle is initiated. The pyruvate returns to the mesophyll cells interact with ATP, and then undergoes a second conversion to phosphoenolpyruvate, the C4 cycle’s starting material. The reducing power of NADPH is subsequently used to transform the oxaloacetate into malate, a different four-carbon molecule. The malate subsequently leaves the mesophyll cells and enters the bundle sheath cells’ chloroplasts, which are specialized cells. Here, the four-carbon chemical malate is decarboxylated to yield CO₂, pyruvate, a three-carbon product, and NADPH. As the pyruvate returns to the mesophyll cells and reacts, the CO₂ combines with ribulose bisphosphate and passes through the Calvin cycle.

In the beginning, CAM (“crassulacean acid metabolism”) plants also bind CO₂ to PEP to create OAA. However, CAM plants absorb carbon during the night and then retain the OAA inside huge vacuoles inside the cell, as opposed to storing carbon throughout the day and pumping the OAA to neighboring cells. This enables them to utilize the CO₂ again for the Calvin-Benson cycle throughout the day, when it may be powered by the sun’s energy, but to have the stomates released in the chill of the evening, preventing water loss. Cacti and numerous other succulent plants are examples of CAM plants, which are more prevalent than C4 plants.

Plants have modified their CAM pathway to undertake photosynthesis in stressful situations. Photorespiration is decreased via the CAM pathway. To minimize moisture loss during the daytime, CAM plants have open stomata at nighttime, where they absorb CO₂. The steps in the procedure are as follows: 

In the chlorophyll of the mesophyll cells, Carbon dioxide and PEP would combine to create 4 carbon oxaloacetate (the same as C4 plants) as the initial stage in the absorption of CO₂. PEPcarboxylase is the catalyst for the process. This takes place at night. Malate and other C4 acids are produced by converting oxaloacetate. Malate is kept overnight in vacuoles. Stomata are sealed daytime, thus there is no gas exchange. The decarboxylation procedure moves malate from the vacuole and lets CO₂ out.

Finally, this Carbon dioxide reaches the Calvin cycle, completing the carbon fixation process. The CO2 that builds up surrounding RuBisCO reduces photorespiration and improves the efficiency of the photosynthetic activity.

Examples 

Most CAM plants are xerophytic. Some water plants, like Hydrilla, Vallisneria, etc., also have CAM pathways. Due to a lack of CO₂, the CAM pathway develops in aquatic plants. Due to slower diffusion in water, the supply of carbon dioxide is constrained. Aquatic CAM plants absorb CO₂ at night when other photosynthetic plants are less active.

Various species of Bromeliaceae, as well as orchids, cacti, pineapple, and moringa.

Differences between C3, C4, and CAM plants

C3 plants	C4 plants	CAM plants
This mechanism is seen in C3 crops, in which  3-phosphoglyceric acid would be the main energy-producing byproduct of solar after carbon-grasping.	Before the C3 cycle, certain crops convert solar energy to oxaloacetic acid, which is then turned into energy. They are referred to as C4 plants. C4 is the route.	Crops that collect the sun’s radiation and later transform it into power at nighttime are known as CAM plants, and indeed the route is also known as the CAM process.
Plants that undergo the first process of photosynthesis	C4 plants are the tropical	Cam plants are semi-dry in nature
Cells would be the mesophyll	Cells would be bundle sheath and also the mesophyll	Only mesophyll in c3 and in the case of c4 both
Photorespiration would be seen at greater rates	Photorespiration is low	Only seen at night times
Compensation point of the co2 Thirty to seventy	six to ten in c4 plants	At night 0.5 in cam plants
Co2:ATP: NADPH2 ratio would be 1:3:2 in c3 plants	Co2:ATP: NADPH2 ratio would be 1:5:2 in c4 plants	Co2:ATP: NADPH2 ratios would be 1:6:5:2 in cam plants
Examples would be cotton, the beans	Examples would be sugarcane	Examples would be orchids
First product would be 3-PGA	First product would be OAA	In C3 3-PGA IN C4 OAA

FAQs on CAM Plants

Question 1: Why the cam pathway starts at night?

Answer:

The CAM pathway begins at night, whenever the temperature drops. This is because of the process that lessens evapotranspiration moisture loss. Therefore it takes place at night.

Question 2: Where would malate be stored in the case of CAM plants?

Answer:

Malate, an organic molecule with four carbons, is created from CO₂. This is kept in the vacuoles, from where it is eventually transferred to the chloroplast for the photosynthetic process of turning malate into CO2.

Question 3: How many genera belonging to aquatic would undergo the CAM pathway?

Answer:

Watery plants are capable of CAM photosynthesis as well. About four plant genera exist. They take the same route as CAM plants that grow on land.

Question 4: Which is known as the facultative CAM plant?

Answer:

A facultative CAM plant is the typical ice plant. When it’s in stress conditions like dehydration or Carbon dioxide, it engages in CAM photosynthesis, which is something it typically never does.

Question 5: What would the CAM plant do during daytime and nighttime?

Answer:

Acidification is the process by which plants absorb Carbon dioxide at nighttime and transform this into organic compounds. They use the organic compounds during the day to create CO2 again, a process called as deacidification.