Question

Members of family Crassulaceae perform
A. ${{C}_{3}}$ photosynthesis
B. CAM photosynthesis
C. ${{C}_{4}}$ photosynthesis
D. All of the above

Answer 1

The Crassulaceae plants family are also known as the stonecrop family. They are various families of dicotyledon flowering plants which are characterized by the presence of succulent leaves and a unique form of photosynthesis. Crassulaceae plants are generally herbaceous but there are some shrubs and a few treelike or aquatic plants.

Complete answer:
- ${{C}_{3}}$ photosynthesis: ${{C}_{3}}$ carbon fixation is the most common carbon fixation metabolic pathway. This process converts carbon dioxide and ribulose bisphosphate into two molecules of 3-phosphoglycerate. This reaction takes place in all the plants as the first step of the Calvin cycle. The plants that take part in the ${{C}_{3}}$ cycle are generally found in areas where the intensity of sunlight is normal, temperatures are normal, carbon dioxide concentrations are higher. This process is found in the plants of tobacco, soybeans, potatoes etc.
- CAM photosynthesis: The members of the Crassulaceae are called CAM plants because they go through the crassulacean acid metabolism. It is the carbon fixation pathway which evolved in some plants as an adaptation to dry conditions. In a plant using full CAM, the stomata in the leaves remain closed during the day to reduce the rate of transpiration but open at night to collect carbon dioxide. The carbon dioxide is stored as the four-carbon acid malate and which are used during the process of photosynthesis at the day.
- ${{C}_{4}}$ photosynthesis: Plants that are adapted to dry tropical regions have the ${{C}_{4}}$ pathway. They possess a special type of lead anatomy, they tolerate high temperatures, they show a response to high light intensity and they do not have a process name photorespiration. They contribute more to the productivity of biomass. The end product of ${{C}_{4}}$ photosynthesis is 4-carbon compound oxaloacetic acid.
Hence, the correct answer is, ‘B.CAM photosynthesis’.

Note: The observations related to the CAM plants were first made by de Saussure in 1804. Benjamin Heyne in 1812 noticed that Bryophyllum leaves in India were acidic in the morning and tasteless by afternoon.