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Plant growth and development: NEET MCQs with answers

105 questions on this topic of Plant Physiology (NEET 2027 syllabus). Here are 12; tap one to see its answer and explanation.

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easy

1. 2,4-D is widely used to:

  1. Induce seed dormancy
  2. Promote fruit ripening
  3. Delay leaf senescence
  4. Kill dicotyledonous weeds without affecting mature monocot plants
Show answer and explanation

Answer: (D) Kill dicotyledonous weeds without affecting mature monocot plants

The synthetic auxin 2,4-D is a herbicide that kills dicot weeds but does not affect mature monocotyledonous plants. It is used to prepare weed-free lawns.

NCERT Class 11

medium

2. Match Column-I with Column-II. Column-I: (A) Auxin (B) Gibberellin (C) Cytokinin (D) Abscisic acid Column-II: (i) Delay of leaf senescence (ii) Stomatal closure (iii) Bolting in cabbage (iv) Apical dominance

  1. A-(iv), B-(iii), C-(i), D-(ii)
  2. A-(iii), B-(iv), C-(i), D-(ii)
  3. A-(iv), B-(i), C-(iii), D-(ii)
  4. A-(ii), B-(iii), C-(i), D-(iv)
Show answer and explanation

Answer: (A) A-(iv), B-(iii), C-(i), D-(ii)

Auxin causes apical dominance, gibberellin causes bolting, cytokinin delays senescence, and ABA closes stomata.

hard

3. Given below are two statements. Statement I: Kinetin occurs naturally in plants. Statement II: Zeatin was isolated from corn kernels and coconut milk. Choose the correct answer.

  1. Both Statement I and Statement II are correct
  2. Statement I is correct but Statement II is incorrect
  3. Statement I is incorrect but Statement II is correct
  4. Both Statement I and Statement II are incorrect
Show answer and explanation

Answer: (C) Statement I is incorrect but Statement II is correct

Kinetin, obtained from autoclaved herring sperm DNA, does not occur naturally in plants. Zeatin, a natural cytokinin, was isolated from corn kernels and coconut milk.

medium

4. Increased vacuolation, cell enlargement and new cell wall deposition are characteristic of the:

  1. Meristematic phase
  2. Phase of maturation
  3. Lag phase only
  4. Phase of elongation
Show answer and explanation

Answer: (D) Phase of elongation

Cells just behind the meristem form the zone of elongation, showing increased vacuolation, cell enlargement and new cell wall deposition. Further away lies the zone of maturation.

NCERT Class 11

easy

5. Which of the following growth regulators promotes female flowers in cucumbers, thereby significantly increasing yield?

  1. Gibberellic acid
  2. Ethylene
  3. Abscisic acid
  4. Cytokinin
Show answer and explanation

Answer: (B) Ethylene

Ethylene promotes feminization (development of female flowers) in cucumber plants, which increases crop yield. Gibberellins, in contrast, promote male flower formation in certain plants.

hard

6. In a sigmoidal growth curve of an annual plant, which of the following events marks the transition from the exponential (log) phase to the stationary phase?

  1. Rapid elongation of newly divided cells
  2. Activation of meristematic cells
  3. Limitation of nutrient and space resources
  4. Loss of capacity for dedifferentiation
Show answer and explanation

Answer: (C) Limitation of nutrient and space resources

In geometric growth, exponential cell division occurs as long as resources are unlimited. The stationary phase is reached when nutrient supply, water, or physical space become limited, leading to a slowing down of the growth rate.

medium

7. Read the following statements regarding the physiological effects of plant growth regulators: Statement I: Gibberellins cause fruits like apple to elongate and improve their shape. Statement II: Cytokinins help overcome apical dominance and promote nutrient mobilisation which helps delay leaf senescence. In light of the above statements, choose the correct answer from the options given below:

  1. Both Statement I and Statement II are correct
  2. Statement I is correct but Statement II is incorrect
  3. Statement I is incorrect but Statement II is correct
  4. Both Statement I and Statement II are incorrect
Show answer and explanation

Answer: (A) Both Statement I and Statement II are correct

According to NCERT, gibberellins (GA) cause fruits like apple to elongate and improve their shape. Cytokinins stimulate lateral bud growth to counteract apical dominance and promote nutrient mobilisation, thereby delaying leaf senescence.

hard

8. Assertion (A): Ethylene is a gaseous plant growth regulator. Reason (R): Ethylene promotes seed dormancy and inhibits germination. Choose the correct option.

  1. Both A and R are true and R is the correct explanation of A
  2. Both A and R are true but R is not the correct explanation of A
  3. A is true but R is false
  4. A is false but R is true
Show answer and explanation

Answer: (C) A is true but R is false

Ethylene is a simple gaseous PGR, but it breaks seed and bud dormancy; it is ABA that promotes dormancy.

hard

9. In most situations, ABA acts as an antagonist to:

  1. Ethylene
  2. Gibberellins
  3. Cytokinins in all cases
  4. Auxins only in roots
Show answer and explanation

Answer: (B) Gibberellins

ABA acts as an antagonist to GAs; for example, ABA promotes seed dormancy whereas GAs promote germination.

medium

10. Consider two leaves, A and B. Leaf A grows from an initial surface area of 5 cm² to 10 cm² in a given time interval. Leaf B grows from an initial surface area of 50 cm² to 55 cm² in the same time interval. What are their respective absolute and relative growth rates?

  1. Both have equal absolute growth rates, but Leaf A has a higher relative growth rate
  2. Both have equal relative growth rates, but Leaf B has a higher absolute growth rate
  3. Leaf A has both higher absolute and relative growth rates than Leaf B
  4. Leaf B has higher absolute growth rate, but Leaf A has higher relative growth rate
Show answer and explanation

Answer: (A) Both have equal absolute growth rates, but Leaf A has a higher relative growth rate

Absolute growth rate is the measurement of total growth per unit time: Leaf A grew by (10 - 5) = 5 cm², Leaf B grew by (55 - 50) = 5 cm², so both have equal absolute growth rates. Relative growth rate is growth per unit initial parameter: for Leaf A it is 5/5 = 100%, whereas for Leaf B it is 5/50 = 10%. Thus, Leaf A has a much higher relative growth rate.

medium

11. Abscisic acid (ABA) is called the stress hormone because it:

  1. Promotes fruit ripening
  2. Breaks seed dormancy
  3. Promotes cell division during stress
  4. Increases tolerance of plants to stresses and causes stomatal closure
Show answer and explanation

Answer: (D) Increases tolerance of plants to stresses and causes stomatal closure

ABA stimulates stomatal closure and increases tolerance to various stresses. It also induces seed dormancy and acts generally as an antagonist to gibberellins.

NCERT Class 11

medium

12. Among their effects on plants, cytokinins help to:

  1. Overcome apical dominance and delay leaf senescence
  2. Induce stomatal closure
  3. Promote abscission
  4. Promote apical dominance
Show answer and explanation

Answer: (A) Overcome apical dominance and delay leaf senescence

Cytokinins promote lateral shoot growth (overcoming apical dominance), new leaves, chloroplasts in leaves and nutrient mobilisation, which delays leaf senescence.

NCERT Class 11

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