Biology [1 Mark Question Answer]

Plants begin to die when concentrated solution of a fertilizer is given to potted plants because fertilizer along with soil water act as a hypertonic solution resulting in exosmosis.

Plants die when salt is sprinkled over them due to plasmolysis of cells. The salt makes the solution hypertonic inside the plant cells which lead to shrinkage of cells or exosmosis.

Ascent of sap is the movement of water from the roots to the upper part of the plant.

The leaves of the wilted lettuce become crisp when kept in cold water because they take up water due to endosmosis in hypotonic solution.

Saline water is hypertonic. So any infectious agent such as bacteria in the throat gets plasmolysed and this cures the infection.

The raisins swell up when placed in water because the water is hypotonic as compared to the raisins so the water enters inside the raisins as a result of endosmosis.

Endosmosis

Plasmolysis

Xylem

Diffusion

Endosmosis

Endosmosis

Plasmolysis

Xylem

Active absorption

Cohesive force

Isotonic solutions

Osmotic pressure

(i) Roots help in the absorption of water.
(ii) They also help in the absorption of minerals.

Root hairs absorb maximum water because in this region, the xylem is not fully mature but the epidermis and endodermis are still permeable to water.

Permeability is the property of a membrane to allow the passage of both solute and solvent molecules.

The pressure of water developed inside the roots due to active absorption of water when transpiration is very low and the rate of absorption is high is known as root pressure.

If the soil was watered with extremely concentrated solution of sodium chloride, the water will move out from the root hair due to osmosis and thus, plasmolysis will take place.

The cytoplasm contains vacuoles having cell sap or solution of mineral salts. This cell sap being more concentrated than the soil solution help in water absorption by endosmosis.

Plasmolysis - The shrinkage of cytoplasm of a living cell as a result of exosmosis is known as plasmolysis.

Hypertonic solution - A solution whose concentration is more than that of cell sap is called hypertonic solution.

Turgor Pressure - It is the actual hydrostatic pressure developed inside a cell as a result of entry of water into it.

Diffusion - It is the movement of molecules or ions from a region of higher concentration to a region of lower concentration to equalize the concentration of the two regions.

Osmosis - Osmosis is the movement of solvent molecules from a region of higher concentration to a region of lower concentration through a semi-permeable membrane.