NEET Practice Questions (MCQs) with Answers & Solutions

Collenchyma is called a living mechanical tissue because it provides support to growing parts of the plant while being flexible and living. Its cells have thickened cell walls which help in mechanical support without impeding growth.

Collenchyma cells are characterized by the deposition of pectin and hemicellulose in their cell walls. This deposition provides flexibility and mechanical support to the plant, especially in areas of growth.

In collenchyma tissue, the thickening of the cell walls occurs due to the deposition of cellulose, hemicellulose, and pectin, which happens only at the corners of the cells. This results in the cells being thickened at the edges and provides mechanical support without restricting growth.

Lignin is a complex organic polymer that hardens and strengthens the cell walls of plants. It is present in stone cells, sclerenchymatous fibers, and tracheids but is absent in sieve cells. Sieve cells, which are part of the phloem tissue, facilitate the transport of nutrients and are not lignified, allowing for flexibility and efficient transport.

Bulliform cells are large, thin-walled cells found in the leaves of grasses, such as maize. These cells help in the rolling and unrolling of leaves to minimize water loss during drought conditions.

In hydrophytes, or aquatic plants, stomata are usually absent or rudimentary because these plants absorb water and nutrients directly from their surrounding environment. Therefore, they do not require well-developed stomata for gas exchange.

Collenchyma tissue provides elasticity and structural support to young stems and leaves. It has thickened cell walls that allow for flexibility and growth, unlike other tissues such as sclerenchyma, which provides rigidity.

Collenchyma is typically absent in roots. Collenchyma cells provide support and are usually found in the stems and leaves of dicot plants, but they are not commonly found in roots. Roots mainly contain parenchyma, sclerenchyma, and various types of meristematic tissues.

Collenchyma tissue is absent in monocots. Monocot plants generally have a simpler vascular structure and do not have the thickened, flexible cell walls of collenchyma which are essential for support in dicots.

Sclerenchyma is the simple permanent tissue formed of dead cells. These cells have thick lignified walls and function primarily to provide structural support to the plant.