Botany MCQs for NEET — Practice Questions with Answers

The exarch condition of xylem, where the protoxylem is located towards the periphery and metaxylem towards the center, is typically found in roots. This arrangement is essential for the conduction of water and nutrients from the soil to the rest of the plant.

Endodermis is a layer of cells that is typically present in roots and helps in regulating the flow of water and minerals into the vascular tissue. It is usually absent in monocot stems, which lack this specialized layer.

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.