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Plant Growth and Development

40 NEET-UG practice questions on Plant Growth and Development, part of Botany. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

  1. Question 1 · Easy

    A root elongates at a constant rate, with only one daughter cell of each division continuing to divide. Which equation describes this growth?

    1. ALₜ = L₀ × rt
    2. BLₜ = L₀ + rt
    3. CW₁ = W₀e^(rt)
    4. DLₜ = L₀ − rt
    Show answer

    Answer: B · Lₜ = L₀ + rt

    When only one daughter cell keeps dividing, length rises at a constant rate. This is arithmetic growth, and it gives a straight line on a graph of length against time.

    • A: Multiplying gives zero length at time zero, which is not arithmetic growth.
    • C: This exponential form describes geometric growth, with both daughter cells dividing.
    • D: A minus sign would mean the root shortens with time.

    Remember this

    Arithmetic growth gives a straight line with Lₜ = L₀ + rt; geometric growth gives a sigmoid curve with W₁ = W₀e^(rt).

  2. Question 2 · Medium

    In one day, leaf P grows from 8 cm² to 12 cm², while leaf Q grows from 40 cm² to 44 cm². Which comparison is correct?

    1. ASame absolute growth and same relative growth
    2. BSame relative growth, and the absolute growth of Q is five times that of P
    3. CSame absolute growth, and the relative growth of P is five times that of Q
    4. DSame absolute growth, and the relative growth of Q is five times that of P
    Show answer

    Answer: C · Same absolute growth, and the relative growth of P is five times that of Q

    Both leaves gain 4 cm², so absolute growth is equal. Relative growth is P = 4/8 = 50% and Q = 4/40 = 10%, and 50/10 = 5.

    • A: Relative growth differs, at 50% and 10%.
    • B: Absolute gain is equal, at 4 cm² each.
    • D: This divides by size wrongly, as the smaller leaf has the higher relative rate.

    Remember this

    Relative growth divides the gain by the previous size, so a small leaf with the same gain has the higher rate.

  3. Question 3 · Medium

    Match List-I with List-II. List-I (regulator) A. IBA B. GA₃ C. Cytokinin D. Ethephon List-II (use or effect) I. Hastens ripening of tomatoes and apples II. Initiates rooting in stem cuttings III. Elongates grape stalks IV. Helps overcome apical dominance

    1. AA-II, B-III, C-IV, D-I
    2. BA-III, B-II, C-IV, D-I
    3. CA-I, B-III, C-IV, D-II
    4. DA-II, B-IV, C-III, D-I
    Show answer

    Answer: A · A-II, B-III, C-IV, D-I

    IBA is an auxin used for rooting of cuttings. Gibberellins lengthen grape stalks. Cytokinins promote lateral shoot growth and so overcome apical dominance. Ethephon releases ethylene, which hastens fruit ripening.

    • B: This swaps the uses of auxin and gibberellin.
    • C: This swaps the uses of auxin and ethephon.
    • D: This swaps the uses of gibberellin and cytokinin.

    Remember this

    Ethephon is the main ethylene source in agriculture because it is absorbed and transported, then releases ethylene slowly.

  4. Question 4 · Hard

    A seedling grows geometrically with r = 0.07 per day. How long does its dry weight take to rise from 5 g to 20 g? Take ln 2 = 0.7.

    1. A20 days
    2. B214 days
    3. C30 days
    4. D10 days
    Show answer

    Answer: A · 20 days

    W₁ = W₀e^(rt), so rt = ln(20/5) = ln 4 = 2 × 0.7 = 1.4, and t = 1.4/0.07 = 20 days. Check by doublings: one doubling takes 0.7/0.07 = 10 days, and 5 g to 10 g to 20 g is two doublings, which is 20 days.

    • B: This uses arithmetic growth, 15/0.07, instead of the exponential form.
    • C: This counts three doublings, which would reach 40 g.
    • D: This counts only one doubling.

    Remember this

    In geometric growth, doubling time is ln 2 divided by r, and it stays constant during the log phase.

  5. Question 5 · Medium

    Consider these statements on ethylene. A. It promotes apical hook formation in dicot seedlings. B. It promotes root hair formation. C. It delays fruit ripening. D. It promotes male flowers in cucumbers. Which of these are correct?

    1. AA and B only
    2. BB, C and D only
    3. CA, B and C only
    4. DC and D only
    Show answer

    Answer: A · A and B only

    Ethylene gives apical hooks in dicot seedlings and raises root hair formation. It hastens fruit ripening, and in cucumbers it promotes female flowers and so raises yield. Hence only A and B hold.

    • B: C and D are false, and A has been left out.
    • C: C is false, because ethylene hastens ripening.
    • D: Both C and D reverse the true effects.

    Remember this

    Ethylene hastens ripening, abscission and senescence; in cucumbers it promotes female flowers.

  6. Question 6 · Easy

    Which sequence of phases does a sigmoid growth curve show?

    1. AStationary, log, lag
    2. BLog, lag, stationary
    3. CLag, stationary, log
    4. DLag, log, stationary

    Answer and explanation in LearnFree account

  7. Question 7 · Medium

    Given below are two statements: Statement I: Interfascicular cambium and cork cambium arise when differentiated parenchyma cells regain the power to divide. Statement II: Cells formed by such dedifferentiated meristems may lose the capacity to divide and mature again, which is called redifferentiation. Choose the correct answer.

    1. ABoth Statement I and Statement II are incorrect
    2. BBoth Statement I and Statement II are correct
    3. CStatement I is incorrect but Statement II is correct
    4. DStatement I is correct but Statement II is incorrect

    Answer and explanation in LearnFree account

  8. Question 8 · Medium

    Arrange these regions in the order met when moving upward from the very tip of a root. A. Region of elongation B. Root cap C. Region of maturation D. Meristematic region

    1. AD, B, A, C
    2. BB, D, A, C
    3. CB, A, D, C
    4. DB, D, C, A

    Answer and explanation in LearnFree account

  10. Question 10 · Hard

    Assertion A: Abscisic acid stimulates the closure of stomata during water stress. Reason R: Abscisic acid helps seeds to withstand desiccation and enter dormancy. Choose the correct answer.

    1. ABoth A and R are correct but R is not the correct explanation of A
    2. BA is correct but R is not correct
    3. CA is not correct but R is correct
    4. DBoth A and R are correct and R is the correct explanation of A

    Answer and explanation in LearnFree account

  11. Question 11 · Hard

    Three similar shoots are treated as follows. P: the shoot tip is removed. Q: the shoot tip is removed and auxin paste is applied to the cut end. R: the tip is left on, and cytokinin is applied to a lateral bud. In which shoots do the lateral buds grow out?

    1. AP and R only
    2. BQ and R only
    3. CP, Q and R
    4. DP only

    Answer and explanation in LearnFree account

  12. Question 12 · Medium

    Pea shoots received the four treatments named under the bars, and lateral bud length was measured after a week. Paste S carries the hormone normally produced at the shoot apex. Going by the result, which hormone is it?

    Figure: MedExams
    Bar chart of lateral bud length under four treatments: intact shoot, tip cut off, cut with plain paste, cut with paste S.
    1. AAuxin
    2. BGibberellin
    3. CAbscisic acid
    4. DCytokinin

    Answer and explanation in LearnFree account

  13. Question 13 · Medium

    Assertion A: The figure shows that leaf X has a higher relative growth rate than leaf Y even though leaf X gains less area. Reason R: Relative growth rate is the growth per unit time expressed per unit initial parameter. Choose the correct answer.

    Figure: MedExams
    Bar chart of the area of two leaves, X and Y, on day 0 and day 1.
    1. ABoth A and R are correct but R is not the correct explanation of A
    2. BBoth A and R are correct and R is the correct explanation of A
    3. CA is correct but R is not correct
    4. DA is not correct but R is correct

    Answer and explanation in LearnFree account

  14. Question 14 · Medium

    Match List-I with List-II. List-I (Plant growth regulator) A. Auxin B. Gibberellin C. Ethylene D. Abscisic acid List-II (Clue from its discovery) I. A volatile given off by ripened oranges hastened the ripening of stored bananas II. Isolated by F.W. Went from tips of oat coleoptiles III. Inhibitor-B, abscission II and dormin proved to be the same compound IV. Bakanae disease of rice seedlings Choose the correct answer.

    1. AA-II, B-IV, C-I, D-III
    2. BA-II, B-I, C-IV, D-III
    3. CA-III, B-IV, C-I, D-II
    4. DA-IV, B-II, C-I, D-III

    Answer and explanation in LearnFree account

  15. Question 15 · Hard

    Leaf shape can differ within one plant. Which of these statements about such heterophylly and plant development are correct? A. Juvenile leaves of cotton and coriander differ in shape from the leaves of the mature plant. B. Buttercup leaves formed in air differ from those formed under water because of the age of the plant. C. In larkspur, the leaves of the juvenile plant differ in shape from those of the mature plant. D. Differentiation in plants is open: cells arising from the same meristem can have different structures at maturity. Choose the correct answer.

    1. AB, C and D only
    2. BA, B and D only
    3. CA, C and D only
    4. DA, B, C and D

    Answer and explanation in LearnFree account

  16. Question 16 · Easy

    In the brewing industry, which plant growth regulator is used to speed up the malting process?

    1. AGibberellin
    2. BCytokinin
    3. CAbscisic acid
    4. DEthylene

    Answer and explanation in LearnFree account

  17. Question 17 · Medium

    Assertion A: Ethephon is sprayed to hasten the ripening of tomatoes and apples. Reason R: An aqueous solution of ethephon is readily absorbed and transported within the plant and releases ethylene slowly. Choose the correct answer.

    1. AA is correct but R is not correct
    2. BBoth A and R are correct but R is not the correct explanation of A
    3. CBoth A and R are correct and R is the correct explanation of A
    4. DA is not correct but R is correct

    Answer and explanation in LearnFree account

  18. Question 18 · Medium

    Which of these statements about abscisic acid are correct? A. It stimulates closure of stomata in the epidermis. B. It increases the tolerance of plants to various kinds of stress. C. It promotes the germination of seeds. D. It acts as an antagonist to gibberellins. Choose the correct answer.

    1. AA, B and C only
    2. BB, C and D only
    3. CA and D only
    4. DA, B and D only

    Answer and explanation in LearnFree account

  19. Question 19 · Medium

    Given below are two statements: Statement I: Spraying sugarcane with gibberellins lengthens the stem and can raise the yield by as much as 20 tonnes per acre. Statement II: Gibberellins inhibit bolting in beet and cabbage. Choose the correct answer.

    1. AStatement I is incorrect but Statement II is correct
    2. BBoth Statement I and Statement II are incorrect
    3. CStatement I is correct but Statement II is incorrect
    4. DBoth Statement I and Statement II are correct

    Answer and explanation in LearnFree account

  20. Question 20 · Easy

    Deep water rice plants keep their leaves above a rising flood by rapid elongation of internodes and petioles. Which plant growth regulator promotes this response?

    1. AEthylene
    2. BAbscisic acid
    3. CIndole-3-butyric acid
    4. DCytokinin

    Answer and explanation in LearnFree account

  21. Question 21 · Medium

    Given below are two statements: Statement I: In cotton, coriander and larkspur, leaves of the juvenile plant differ in shape from those of the mature plant, an example of heterophylly caused by the environment. Statement II: Living differentiated cells that have lost the ability to divide can regain it, as when interfascicular cambium arises from parenchyma; this is dedifferentiation. Choose the correct answer.

    1. ABoth Statement I and Statement II are incorrect
    2. BStatement I is correct but Statement II is incorrect
    3. CBoth Statement I and Statement II are correct
    4. DStatement I is incorrect but Statement II is correct

    Answer and explanation in LearnFree account

  22. Question 22 · Medium

    Under steady conditions, a root elongates at a constant rate. It is 3 cm long on day 0 and 9 cm long on day 4. Assuming the rate stays the same, how long will it be on day 10?

    1. A25.5 cm
    2. B22.5 cm
    3. C18 cm
    4. D15 cm

    Answer and explanation in LearnFree account

  23. Question 23 · Medium

    Match List-I with List-II. List-I (plant part) A. Maize root apical meristem B. Watermelon fruit cells C. Pollen tube D. Dorsiventral leaf List-II (parameter that best expresses its growth, as NCERT describes it) I. Increase in cell size II. Increase in surface area III. Increase in cell number IV. Increase in length

    1. AA-IV, B-I, C-III, D-II
    2. BA-III, B-I, C-II, D-IV
    3. CA-I, B-III, C-IV, D-II
    4. DA-III, B-I, C-IV, D-II

    Answer and explanation in LearnFree account

  24. Question 24 · Easy

    Foresters want young conifer trees to reach maturity sooner and bear seed early. Spraying the juvenile trees with which group of growth regulators achieves this?

    1. AGibberellins
    2. BAuxins
    3. CCytokinins
    4. DAbscisic acid

    Answer and explanation in LearnFree account

  25. Question 25 · Hard

    Read the following statements about plant growth regulators. A. Gibberellins cause bolting, the internode elongation just before flowering, in beet and cabbage. B. Auxins prevent the abscission of older, mature leaves and fruits. C. Ethylene promotes rapid internode elongation in deep-water rice, keeping the upper shoot above water. D. Cytokinins hasten leaf senescence. Which of these are correct?

    1. AC and D only
    2. BA, C and D only
    3. CA and C only
    4. DA, B and C only

    Answer and explanation in LearnFree account

15 more Plant Growth and Development questions

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