Question

Passive absorption of water from the soil is mainly affected by
(a) Tissue organization of root
(b) Sucking power of root hairs
(c) Tension of cell sap due to transpiration
(d) Osmotic concentration of cell sap

Answer 1

Hint: Passive absorption which does not involve any expenditure of energy for the transportation of water from the soil to the roots mainly occurs using the mechanism of difference in a concentration gradient.

Complete answer:
Osmosis refers to the movement of the solvent due to the presence of a concentration gradient across the semipermeable membrane. The solution turns to flow from the part having a high concentration gradient to the part having the low concentration gradient with an aim to equalize the concentration. The roots of the plants use this mechanism to absorb water from the soil. Transpiration which creates a negative pressure and the solvent particles that is the water moves from the roots to the extreme parts like the leaves. Due to which there is a low concentration always at the root ends concerning the amount of water present in the soil or the concentration of the soil. This condition is sufficient for osmosis to occur and water to enter the root takes you to the concentration gradient formed.

Additional Information:
- Osmosis always takes place across from your membrane and it requires a gradient concentration gradient to be formed across the semipermeable membrane too.
- Osmosis is a beneficial process as it is not an active mode of transportation and does not involve any kind of expense of energy due to which the plants can take up water easily without consuming any form of energy.
- The ascent of sap which is occurring in the plant continuously as to the process of osmosis as it helps the planned to maintain a concentration gradient at the root tips which also helps the water to move into the root due to the difference in consideration.
So, the correct option is, “Osmotic concentration of cell sap”.

Note:
- The semi-permeable membrane does not allow molecules that are larger like polysaccharides to pass.
- As plants use a large amount of water osmosis is the only way for them to transport water, otherwise, future energy will be lost in the process of transportation of water.