Question

Onion peel is used to demonstrate
A. Peeling
B. Lysis
C. Plasmolysis
D. Division

Answer 1

Hint:- Onions are formed as bulbs underground. It is used as a vegetable. It is arranged as many layers or scales which are modified leaves. They are formed underground and the leaves are modified for storage. The inner part of the onion contains fleshy leaves or scales, while the outer layers are dry and membranous. Onions have epidermal layers that are protective in function. They have thin and transparent skin layers that are used for demonstrating plant anatomy.

Complete Answer:- Plasmolysis occurs when water moves out of the cells and the cell membrane moves away from the cell wall of a plant cell. Plasmolysis can be demonstrated by using onion peel. A layer of onion peel placed in a hypertonic solution is taken in a microscopic slide, a wet mount is prepared and observed under the microscope by using iodine stain.
When any hypertonic solution like sucrose solution is added to the onion peel, water molecules present inside the onion cells move outward causing plasmolysis. Water molecules move out of the cytoplasm first and then from the vacuole. The major part of a plant cell is occupied by the vacuole. As the water moves out of the cell by diffusion, the protoplasm shrinks and moves away from the cell wall. The cell then becomes plasmolyzed. When water is added to a plasmolyzed cell, water molecules enter inside the cell again by diffusion causing deplasmolysis.
Lysis is the destruction or disintegration of cells due to injury or rupture of the cell membrane or cell wall. It is a process and cannot be observed in onion peel. A lysed onion cell can be observed. Peeling is the removal of the outer layer of a vegetable skin or any outer covering. The division of cells is the process by which daughter cells are produced from parent cells.

The correct answer is Option C.

Note:- Onion cells and human cheek cells are usually used for the demonstration of the anatomy of plant and animal cells, respectively. Onion cells are rectangular, brick-shaped cells while human cells are round shaped. A hypertonic solution contains higher solute concentration and a hypertonic solution has higher solvent concentration. In a plasmolyzed cell, the space between the shrunken protoplasm and cell wall is occupied by the hypertonic solution.