Question

Collenchymatous hypodermis is a characteristic feature of
(a) Dicot stem
(b) Monocot stem
(c) Monocot as well as dicot stem
(d) Hydrophytes

Answer 1

Hint: The hypodermis is the layer of cells that lie just adjacent and inner to the upper exposed epidermal layers. Collenchyma is a type of simple permanent tissue that forms the hypodermis in plants whose anatomy includes vascular bundles arranged in broken rings.

Complete answer:
The hypodermis is usually present in stems and absent in young roots. In mature roots, they are replaced by thick- walled exodermis. They are usually two to three cell layers thick and are followed by parenchymatous cells that make up the cortex in the stem. In dicot stems, collenchymatous hypodermis is observed. Collenchyma is a simple permanent tissue with irregular thickenings of pectocellulose in specific areas of their walls. It provides mechanical strength coupled with flexibility.

Additional Information:
- In the monocot stem, the hypodermis is generally sclerenchymatous. Sclerenchymatous tissue is a type of simple permanent tissues with highly thickened walls and extremely narrow cavities. Little or negligible protoplasm may be present. They are supportive in function.
- Hydrophytes are the type of plants that grow in aquatic habitats i.e in a water- rich environment. They can be free-floating or fully submerged.E.g. Pistia.
- The tissue system in plants is of three types based on their location and structure. These are the epidermal tissue system, ground tissue system, and vascular tissue system. The epidermal tissue system is the outermost covering of a whole plant body that includes the epidermal cells, stomata, and epidermal appendages such as trichomes and hairs. They are parenchymatous in nature.
- The ground tissue consists of all the tissue except the epidermis and vascular bundles. The hypodermis is also a type of ground tissue. They may be parenchymatous, collenchymatous, or sclerenchymatous.
In leaves, the ground tissue is represented by thin-walled chlorenchyma. These are referred to as mesophyll.
- Vascular tissue system includes complex permanent tissues i.e xylem and phloem.
So, the correct answer is ‘(a) Dicot stem.’

Note:
- Parenchyma is made up of simple, thin- walled, closely packed, with little intercellular spaces between them. They are the most abundant in plants. Their cell wall contains cellulose with uniform thickening around its periphery.
- Chlorenchyma is a type of parenchyma that bears chloroplasts. Aerenchyma is another form of parenchyma whose cytoplasm is rich in air vacuoles.