NEET Practice Questions (MCQs) with Answers & Solutions

Lenticels are associated with gaseous exchange in plants. They are small, spongy openings in the bark of stems and roots that allow oxygen to enter the plant and carbon dioxide to exit. This process is crucial for respiration and other metabolic activities.

Sieve tube elements are living cells that form part of the phloem tissue in plants, responsible for the transport of nutrients. However, mature sieve tube elements lack a nucleus. Instead, they rely on companion cells to perform necessary cellular functions.

Companion cells are specialized parenchyma cells found in the phloem of flowering plants. They are living and nucleated, and they play a crucial role in the maintenance and function of sieve tube elements, aiding in the transport of substances.

The last produced secondary xylem remains located near the cambium ring. This is because the cambium ring is the region where new xylem and phloem cells are continuously produced in a plant. As the plant grows, older xylem cells are pushed towards the interior, while newer secondary xylem cells stay close to the cambium ring.

In a monocotyledenous stem, the vascular bundles are not arranged in a circle but are usually scattered throughout the ground tissue. There is no clearly defined pith as there is in many dicotyledonous species. As in the dicots the xylem of the bundles is pre-orientated toward the middles of the stem. Maize is a monocot. So, the vascular bundles in maize stem are scattered in ground tissue.