Question

The tall pillar-like mesophyll cells present in the internal parts of the leaf is known as
A. Palisade parenchyma
B. Spongy parenchyma
C. Aerenchyma
D. None of the above

Answer 1

Hint: The pillar-like mesophyll cells help in the process of photosynthesis in the plants. On the other hand, irregularly shaped mesophyll cells help in the process of respiration in plants.

Complete answer:
The leaf is made up of three types of tissues - epidermis, mesophyll, and vascular tissue. The epidermis is the outermost layer present in a leaf that secretes a waxy cuticle, providing protection to the leaf.
The mesophyll tissue layer is sandwiched between two layers of the epidermis. The mesophyll layer is composed of a palisade mesophyll region and spongy parenchyma. Palisade mesophyll consists of columnar cells with spaces between the cells. It is mainly associated with the production of food in plants. Chloroplasts are mostly found in palisade mesophyll. Chloroplasts contain chlorophyll, a green pigment that absorbs energy from sunlight for photosynthesis. They do not have intercellular spaces.
The spongy mesophyll is composed of irregularly shaped cells and are located below the palisade mesophyll. It is associated with the gaseous exchange in leaves as they have large intercellular spaces.
Leaf veins are composed of vascular tissue. The vascular tissue consists of a tube-like structure known as xylem and phloem which helps in the transportation of water and nutrients to flow throughout the leaves and plant respectively.
Aerenchyma is the modification of parenchyma which is surrounded by the air chambers. In these air chambers, oxygen is stored that is produced by photosynthesis and utilized in respiration. It helps in providing buoyancy in hydrophytic plants.

So, the correct answer is option A, palisade parenchyma.

Note: The palisade parenchyma is present towards the upper or adaxial surface of the leaf, so the upper surface of leaves appears more green in color. The spongy parenchyma is present towards the lower or abaxial surface of the leaf.