Question

Give reasons: Wilted lettuce leaves become crisp when placed in cold water for a while.

Answer 1

Osmosis:

I. Osmosis is the movement of water molecules from their higher concentration area to a lower concentration area through a semi-permeable membrane.

II. Tonicity:

1. The capability of an extracellular solution to enable water to migrate into or out of a cell by osmosis is referred to as tonicity.
2. Depending upon their relative concentration, solutions are of three types - hypotonic, hypertonic, and isotonic.

III. The turgidity of cells is maintained through osmosis. Types of Osmosis:

1. Endosmosis - When a cell is submerged in a hypotonic solution, the water moves inside the cell.
2. Exosmosis - When a cell is dipped in a hypertonic solution, the water in the cell flows out, and the cell becomes flaccid.

1. When wilted lettuce leaves are kept in cold water(a hypotonic solution), the leaves take up water due to endosmosis.

2. The cells of the leaves become turgid and crisp due to endosmosis.