Transport in Plants Test 4

A hypotonic solution is any solution that has a lower osmotic pressure than another solution. In the biological fields, this generally refers to a solution that has less solute and more water than another solution.

In a hypotonic solution the total molar concentration of all dissolved solute particles is less than that of another solution or less than that of a cell.

option ( a) is correct. 

Explanation :- 

{ here, all other options except option ( a) are true. 

• Option ( b) water potential of pure water is zero.    

The water potential of pure water in an open container is zero because there is no solute and the pressure in the container is zero. Adding solute lowers the water potential. When a solution is enclosed by a rigid cell wall, the movement of water into the cell will exert pressure on the cell wall.

• Option ( c) movement of water is expressed in terms of free energy.     

    Water moves from an area of higher total water potential (higher Gibbs free energy) to an area of lower total water potential. Gibbs free energy is the energy associated with a chemical reaction that can be used to do work. This is expressed as  ∆Ψ… It is the main driver of water movement in the xylem.

• Option ( d) 

∆G determines the direction and extent of chemical change. Remember that ∆G is meaningful only for changes in which the temperature and pressure remain constant. These are the conditions under which most reactions are carried out in the laboratory.

Therefore, option ( a) is correct.

Water flows from higher water potential to lower water potential. The water potential is calculated by the sum of osmotic potential and pressure potential. Using this formula water potential of cell A comes out to be -10 bars,

whereas the water potential of cell B comes out to be -12 bars. Hence, water will flow from cell A (higher water potential) to cell B (lower water potential).

The process of adsorption of water by solid particles of a substance without forming a solution is called 'imbibition'.

It is a type of diffusion by which movement of water take place along a diffusion gradient.

The solid particles which adsorb water or any other liquid are called imbibants. The liquid which is imbibed is known as imbibate.Cellulose, pectic substances, protoplasmic protein and other organic compound in plant cells show great power of imbibition.

Osmosis is passive transport where water follows down the gradient across a semi-permeable membrane from a higher concentration to a  lower concentration. Reverse osmosis simply means that the cumulative pressure gradients cause the flow of water molecules to go against the osmotic pressure gradient from a lower concentration to the higher concentration. 

As the process of reverse osmosis requires energy for transporting molecules against the concentration gradient, it is an active process.

Hence, Option A is the correct one. 

Hypertonic solution means more solute ie., high concentration of solute & low concentration of water.
Osmosis - diffusion of water from high concentration of water to the low concentration of water.
When compared to the hypertonic sugar solution , cell has high concentration of water .so , when cell is kept in that hypertonic sugar solution , movement of water is from cell to the sugar solution.
Thus the cell loses water and becomes dehydrated.

When cells are in isotonic solution, movement of water out of the cell is exactly balanced by movement of water into the cell.
If concentrations of dissolved solutes are less outside the cell than inside, the concentration of water outside is correspondingly greater. When a cell is exposed to such hypotonic conditions, there is net water movement into the cell. Cells without walls will swell and may burst (lyse)
In hypertonic solutions, concentrations of dissolved solutes are greater outside the cell and so the concentration of water outside is correspondingly lower. As a result, water inside the cell will flow outwards to attain equilibrium, causing the cell to shrink. As cells lose water, they lose the ability to function or divide. 
Thus, the correct answer is option (A).

Exosmosis is a process in which the water molecules move from higher concentration region of the cell to the lower concentration region of surroundings through the cell membrane. Due to this, the cell shrinks. This happens when a cell is kept in hypertonic solution, i.e., a solution with higher solute concentration. Exosmosis is also termed as plasmolysis.

(D) Swelling of seed in soil is an example of imbibition. Imbibition is a type of diffusionprocess along the concentration gradient enabling the solid to absorb water andincrease in volume. When seed is put in the soil it absorbs water which activateenzymes present in seed and this induces the seed germination. The other options, i.e., uptake of water by root hair is an example of absorption,exchange in of gases stamata is an example of diffusion and opening of stomata is anexample of turgor pressure or turgidily.

In a hypoosmotic solution, a plant cell will take up water and become turgid. As long as the plasma membrane is intact, the turgor pressure of a cell is equal and opposite to the wall pressure. This is the main source of structural support in herbaceous plants. Plant cells are enclosed by a rigid cell wall. When the plant cell is placed in a hypotonic solution, it takes up water by osmosis and starts to swell, but the cell wall prevents it from bursting. The plant cell is said to have become turgid i.e., swollen and hard. The pressure inside the cell rises until this internal pressure is equal to the pressure outside. This liquid or hydrostatic pressure called as the turgor pressure prevents further net intake of water.