This set of Botany Written Test Questions and Answers focuses on “Plant-Water Relations-2”.
1. At atmospheric pressure, the water potential is equal to_________
a) Gravitational potential
b) Pressure potential
c) Solute potential
d) Matrix potential
Explanation: For a solution at atmospheric pressure, the water potential is equal to solute potential. Gravitational potential and matrix potential are of negligible importance. Pressure potential is responsible for creating tension in the xylem which leads to water transport up a stem.
2. The pressure built up against the cell wall of a plant cell due to diffusion of water causes the cell to become _________
Explanation: In hypotonic solution, water enters into the resulting in pressure being developed against the wall and the cell becomes turgid. The cell becomes flaccid in isotonic solution, plasmolysed in hypertonic solution and imbibed when imbibition takes place which is also a kind of hypotonic solution activity.
3. Affinity between the absorbent and the liquid is pre-requisite condition for imbibition.
Explanation: For imbibition to take place, there should be water potential gradient between the absorbent and the liquid imbibed. Also, for any substance to carry out imbibition with any other liquid, there must be potential attraction between the absorbent and the liquid.
4. Pressure potential is ________
Explanation: Pressure potential is usually positive but it causes negative potential in the xylem in order to enable water transport up the stem. Water potential of pure water is zero. Solute potential is negative. Gravitational and matrix potential remains relatively constant.
5. The space between the cell wall and the shrunken protoplast in a plasmolysed cell is occupied by ________
a) hypotonic solution
b) hypertonic solution
c) isotonic solution
Explanation: The protoplast shrinks in presence of hypertonic solution, swells in presence of hypotonic solution and becomes flaccid in isotonic condition. Water is helpful in dilution or in bringing isotonic condition.
6. Which of the following is a reversible phenomenon?
Explanation: Only plasmolysis is a reversible phenomenon as the cell can become normal when shifted to hypotonic solution. When the cell is already in hypotonic solution it swells and bursts, therefore, cannot be reversed. Flaccid cell is an ideal cell where there is continuous flow of water in and out of the cell. Imbibition aids in germination which is again a non-reversible process.
7. Seedlings emerge out of the soil into open surroundings due to imbibition.
Explanation: Imbibition is a special type of diffusion which helps solids absorb moisture resulting in increase in volume. In the same way, it provides the required pressure for emergence out of the soil to the tiny seedlings.
8. Imbibition is commonly seen in _____
Explanation: Imbibition is usually found in colloids which can absorb other substances. Liquids and gases are fluids which are absorbed. Suspension is formed in centrifugation.
9. Which of the following is not an important determinant of the movement of molecules in or out of the cell?
a) Cell membrane
b) Thickness of membrane
d) Membrane of vacuole
Explanation: Thickness of membrane has no role to play in the movement of molecules from one region to another. The cell membrane, tonoplast and membrane of the vacuole must be permeable to the substances, hence, are important determinants of the transportation of molecules.
10. Statement A: Osmotic pressure is negative.
Statement B: Osmotic potential is also negative.
a) Both the statements are true
b) Both the statements are false
c) Statement A is true but Statement B is false
d) Statement B is true but Statement A is false
Explanation: Osmotic pressure is the pressure required to prevent diffusion of water in and out of the membrane. Osmotic potential is the energy required to carry out the process of osmosis. Both are numerically same but osmotic pressure is positive while osmotic potential is negative. They depend on the solute concentration.
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