12th biology chapter 6 MCQs (Plant Water Relations)

Q1. In soil, water available for absorption by root is ……………….
    a. gravitaional water
    b. capillary water
    c. hygroscopic water
    d. combined water
Answer: capillary water 
Explanation: Plants absorb water and minerals through roots from the soil for metabolism and their life. This soil water comes to the upper level of the soil through a fine tube-like gap in the soil. So this water is called capillary water. So the correct answer is ‘Capillary water’

Chapter 1:  The Living World

Q2. The most widely accepted theory for the ascent of sap is …………..
    a. capillarity theory
    b. root pressure theory
    c. diffusion
    d. transpiration pull theory
Answer: Transpiration pull theory 
Explanation : Transpiration pull cohesion theory for the ascent of sap in trees is the most widely accepted.

Chapter 5: Morphology of Flowering Plants

Q3. Water movement between the cells is due to ………….
    a. T. P.
    b. W. P.
    c. DPD
    d. incipient plasmolysis
Answer: DPD 
Explanation: Water movement between cells is due to DPD. If a cell is placed in pure water, it shows endosmosis and water enters the cell.

Chapter 7: Structural Organisation in Animals

Q4. In guard cells, when sugar is converted into starch, the stomatal pore ………….
    a. closes almost completely
    b. opens partially
    c. opens fully
    d. remains unchanged
Answer: Closes almost completely.
Explanation: When sugar is converted into starch, the stomatal pore closes completely in guard cells. At night time, the CO2 released during respiration accumulates. As a result, the acidity of the guard cells increases and pH decreases. The decreased pH favors the conversion of sugar to starch.

Chapter 10: Cell Cycle and Cell Division

Q5. Surface tension is due to …………..
    a. diffusion
    b. osmosis
    c. gravitational force
    d. cohesion
Answer: Cohesion 

Chapter 13: Photosynthesis in Higher Plants

Q6. Which of the following types of solution has a lower level of solutes than the solution?
    a. Isotonic
    b. Hypotonic
    c. Hypertonic
    d. Anisotonic
Answer: Hypitonic 
Explanation: A hypotonic solution has a lower concentration of solutes than another solution. In biology, a solution outside of a cell is called hypotonic if it has a lower concentration of solutes relative to the cytosol.

Chapter 14: Respiration in Plants

Q7. During the rainy season wooden doors warp and become difficult to open or close because of ……………
    a. plasmolysis
    b. imbibition
    c. osmosis
    d. diffusion
Answer: Imbibition
Explanation: Humidity increases during the rainy season. because of Imbibition.

Chapter 16: Digestion and Absorption

Q8. Water absorption takes place through…………
    a. lateral roots
    b. root cap
    c. root hair
    d. primary root
Answer: Root Hair
Explanation: Plants absorb water through the entire surface using roots, stems, and leaves. However, mainly the water is absorbed by roots. The area of young roots where most absorption takes place is the root hair zone.

Chapter 18: Body Fluids and Circulation

Q9. Due to low atmospheric pressure the rate of transpiration will………….
    a. increase
    b. decrease rapidly
    c. decrease slowly
    d. remain unaffected
Answer: Increase 
Explanation: If atmospheric pressure is low, water will move out of the plant into the atmosphere as water vapor. Plants will lose water at a higher rate by the transpiration process. Hence, at low atmospheric pressure, the rate of transpiration increases.

Chapter 21: Control and Co-ordination

Q10. Osmosis is a property of ………………
    a. solute
    b. solvent
    c. solution
    d. membrane
Answer: Membrane
Explanation: Osmosis is defined as the movement of solvent or water molecules from a region of their higher concentration to a region of their lower concentration through a semipermeable membrane. Hence, osmosis depends upon the semipermeable nature of the membrane.