Question

In Opuntia, the function of photosynthesis is carried out by
A. Cladode
B. Phylloclade
C. Phyllode
D. Bulb

Answer 1

Hint:- Photosynthesis is a physicochemical process through which the radiant energy of the sun is used by green plants to convert inorganic compounds like carbon dioxide and water into organic compounds like starch.

Complete answer:
In vascular plants, the process of photosynthesis is carried out by flattened structures known as leaves. But in some plants leaves are absent. Instead, stems act as photosynthetic organs. Opuntia is a species of cactus that belongs to the subfamily Opuntioideae. These plants mostly grow in arid soil i.e. areas where the availability of water is very less and the climate is very hot and dry. Thus, these plants are also known as Xerophytic plants. The body of the plant shows certain modifications to survive the harsh climatic conditions. They have leaves that are spine-like and do not perform the process of photosynthesis. This helps them to reduce the rate of transpiration. The stems are green, succulent, thick and flattened. They contain chlorophylls and carry out photosynthesis. These modified stems are known as phylloclades. Apart from the main stem, the branches are also modified to perform photosynthesis. They contain several nodes and internodes and can grow indefinitely. Thus, the entire shoot is collectively represented as a phylloclade.

So, the correct answer is option (B), Phylloclade.

Note:- In Opuntia, phylloclades are adaptations for the xerophytic mode of life. They store food and conserve water by retaining them in the form of mucilage. They have a thick waxy cuticle to prevent excessive loss of water. They also have an alternative photosynthetic pathway known as Crassulacean acid metabolism (CAM). This allows the Opuntia plants to take in atmospheric carbon dioxide during the night time when the loss of water can be minimized.