Question

Assertion :Loss of water produces a negative hydrostatic pressure. Reason: Positive hydrostatic pressure is developed due to osmotic entry of water into it.

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
• C. Assertion is correct but Reason is incorrect.
• D. Both Assertion and Reason are incorrect.

Answer 1

The correct option is B Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.

Hydrostatic pressure is the pressure which develops in an osmotic system due to osmotic entry or exit of water from it. Loss of water produces a negative hydrostatic pressure or tension. It develops in xylem due to loss of water in transpiration. This is very important in transport of sap over long distances in plants. A positive pressure develops in a plant cell or system due to entry of water into it. Positive hydrostatic pressure is also called turgor pressure. Due to turgor pressure the protoplast of a plant cell wall press the cell wall to the outside. The cell wall, being elastic, presses the protoplast with an equal and opposite force. The force exerted by the cell wall over the protoplast is called wall pressure (WP). Normally wall pressure is equal and opposite o turgor pressure except when the cell becomes flaccid.