Question

Given below are diagrams of plant cells as seen under the microscope after having been placed in two different solutions.

1. What is the technical term for the condition of : (a) Cell A (b,) Cell B
2. From the solution given in brackets (water, strong sugar solution, 1% salt solution) name the solution into which : (a) Cell A (b) Cell B, was placed before being viewed under the microscope.
3. Under what conditions in the soil will the root hair cell resemble : (a) Cell A (b) Cell B ?
4. Name the pressure responsible for the movement of water from the root hair cell to the xylem of root. How is it set up ?
5. Name the pressure that helps in movement of water up the xylem of the root.

Answer 1

1. (a) Cell A : Turgidity

• When a cell kept in fresh water, it absorbs water through endosmosis, and finally reach at a state that it can not take more water inside the cell, the cell is stretched and is called turgid, the condition is known as turgidity. In this condition a hydrostatic pressure is generated by cell sap on the cell wall is known as Turgor pressure.

(b) Cell B : Flaccidity

• When the same cell is kept in 5 % salt solution for few minutes, the plasma membrane will withdraw from the cell wall, and protoplasm get shrink, the cell become flaccid and condition is known as flaccidity, this process is known as plasmolysis.
• Flaccidity is reverse of turgidity.

2.(a) Cell A is placed in water, by absorption of water it becomes swell and turgid.

(b) Cell B is placed in 1% salt solution, here salt solution acts as hypertonic solution.

3. (a) Root cell resemble with Cell A in normal condition when roots absorb water (as hypotonic solution) from the soil, and become swell and turgid through endosmosis.

(b)

• Root cell resemble with Cell B in a different condition, when excessive soluble fertilizers are used.
• Excess application of such fertilizers makes the soil solution hypertonic as compare to cell sap.
• Plant losses water and cell gets shrink, hence plant cells begin to die due to plasmolysis.

4. Root pressure is mainly responsible for the movement of water from the root hair cell to the xylem of the root. This pressure is built up due to osmosis.

5. Root pressure :

• The pressure which is developed in root due to inflow of water, which pushes plant sap upwards is called root pressure.
• Firstly water absorbed by root hairs from the soil and collects in cortical cells, hence cortical cells become turgid, in this condition walls of cortical cells exerts pressure on their fluid contents and pushes them towards xylem vessels.
• Now the cortical cell becomes flaccid ,again absorbs water and forces towards xylem.
• Hence the root pressure is one of the force that raise water through the stem in to leaves.