Question Bank — Plant Growth and Development

NCERT Class 11 Biology · Chapter 13 · CBSE Board Pattern

Class 11 Biology Chapter 13 Question Bank CBSE Board Pattern

Section A — MCQs (10 questions, 1 mark each)

  1. Growth in plants is regarded as an irreversible permanent increase in size of an organ or its parts or even of an individual cell. This growth is generally accompanied by
    (a) only anabolic processes
    (b) only catabolic processes
    (c) both anabolic and catabolic metabolic processes
    (d) no metabolic processes

  2. The form of growth in which new cells are continuously added to the plant body by the activity of meristems is called
    (a) closed form of growth
    (b) open form of growth
    (c) determinate growth
    (d) arithmetic growth

  3. Which of the following parameters is used to measure growth at the cellular level?
    (a) Increase in fresh weight only
    (b) Increase in dry weight, length, area, volume and cell number
    (c) Increase in number of leaves only
    (d) Increase in height of the plant only

  4. The phase of growth in which cells proximal to the meristematic zone show increased vacuolation, cell enlargement and new cell wall deposition is
    (a) meristematic phase
    (b) maturation phase
    (c) elongation phase
    (d) differentiation phase

  5. In arithmetic growth, the expression for length at time ‘t’ is given by
    (a) Lt = L0 + rt
    (b) W1 = W0 ert
    (c) Lt = L0 × rt
    (d) W1 = W0 + rt

Assertion-Reason Questions

  1. Assertion (A): Plant growth is indeterminate because of the presence of meristems at certain locations in the plant body.
    Reason (R): The cells of meristems have the capacity to divide and self-perpetuate, while their products soon lose the capacity to divide.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

  2. Assertion (A): Abscisic acid is also called the stress hormone.
    Reason (R): ABA stimulates closure of stomata and increases tolerance of plants to various kinds of stresses.
    (a) Both A and R are true and R is the correct explanation of A.
    (b) Both A and R are true but R is not the correct explanation of A.
    (c) A is true but R is false.
    (d) A is false but R is true.

  3. The phenomenon by which living differentiated cells regain the capacity to divide under certain conditions is termed
    (a) differentiation
    (b) dedifferentiation
    (c) redifferentiation
    (d) maturation

  4. Which of the following represents plasticity in plant development?
    (a) Heterophylly in cotton, coriander and larkspur
    (b) Apical dominance in tea plants
    (c) Secondary growth due to vascular cambium
    (d) Arithmetic growth of roots

  5. The PGR that is largely an inhibitor of growth activities and promotes senescence and abscission is
    (a) auxin
    (b) gibberellin
    (c) cytokinin
    (d) ethylene

Section B — Very Short Answer (6 questions, 2 marks each)

  1. Define growth rate. Differentiate between absolute growth rate and relative growth rate.
  2. What is meant by open differentiation in plants? Give one example.
  3. List any four conditions necessary for growth in plants.
  4. Differentiate between differentiation and dedifferentiation with one example of each.
  5. Why is the sigmoid growth curve typical for cells, tissues and organs of a plant?
  6. Name the two groups into which plant growth regulators are broadly divided on the basis of their functions. Give one example of each group.

Section C — Short Answer (5 questions, 3 marks each)

  1. Describe briefly the three phases of growth in plants with reference to root tips.
  2. Explain the difference between arithmetic and geometric growth with the help of suitable mathematical expressions.
  3. What is plasticity? Explain with examples of heterophylly due to phases of life and due to environment.
  4. Describe the discovery and any three physiological effects of auxins.
  5. Explain the role of ethylene in fruit ripening and any two other physiological processes in plants.

Section D — Long Answer (3 questions, 5 marks each)

  1. Describe the sequence of developmental processes in a plant cell. Explain how growth, differentiation and development are closely related events. Add a note on open differentiation.
  2. Draw a neat labelled diagram of the sigmoid growth curve. Explain the lag, log/exponential and stationary phases. Why is the curve characteristic of living organisms growing in a natural environment?
  3. Describe the physiological effects of any three of the following plant growth regulators: auxins, gibberellins, cytokinins, abscisic acid. Mention one agricultural/horticultural application of each.

Section E — Case/Source-Based (2 questions, 4 marks each)

Case 1

A farmer observes that removing the shoot tip of tea plants results in the growth of lateral branches, making the plants bushier. He also notes that application of a certain PGR helps in increasing the length of grape stalks and hastens maturity in juvenile conifers.

(i) Name the phenomenon observed after removal of the shoot tip and the PGR responsible for it. (1)
(ii) Which PGR would help the farmer increase grape stalk length and hasten maturity in conifers? Give its chemical nature. (1)
(iii) How does the PGR mentioned in (ii) affect the yield of sugarcane? (1)
(iv) Why are PGRs considered intrinsic factors controlling plant development? (1)

Case 2

In a tissue culture laboratory, fully differentiated parenchyma cells are induced to divide and form a mass of undifferentiated cells (callus) under controlled conditions. Later these cells are made to differentiate again into specific tissues.

(i) Identify the phenomenon by which differentiated cells regain the capacity to divide. (1)
(ii) What term is used when these dividing cells again lose the capacity to divide and mature to perform specific functions? (1)
(iii) Name the PGRs that were historically found necessary along with auxins for callus proliferation in tobacco internodal segments. (1)
(iv) How does this ability of plant cells demonstrate that differentiation in plants is open? (1)

▶ Answer Key Attempt all questions first,
then tap to reveal

Section A

  1. (c) — both anabolic and catabolic metabolic processes (1 mark)
  2. (b) — open form of growth (1 mark)
  3. (b) — increase in fresh weight, dry weight, length, area, volume and cell number (1 mark)
  4. (c) — elongation phase (1 mark)
  5. (a) — Lt = L0 + rt (1 mark)
  6. (a) — Both true and R explains A (1 mark)
  7. (a) — Both true and R explains A (1 mark)
  8. (b) — dedifferentiation (1 mark)
  9. (a) — Heterophylly in cotton, coriander and larkspur (1 mark)
  10. (d) — ethylene (1 mark)

Section B

  1. Growth rate: increased growth per unit time (1 mark). Absolute = total growth per unit time; relative = growth per unit time on a common basis (e.g., per unit initial size) (1 mark).
  2. Cells/tissues arising from same meristem attain different structures at maturity depending on position (1 mark); e.g., cells away from root apex become root-cap cells, peripheral cells become epidermis (1 mark).
  3. Water (turgidity and enzymatic medium), oxygen (metabolic energy), essential nutrients (protoplasm synthesis), optimum temperature, light/gravity signals (any four — ½ mark each).
  4. Differentiation: maturation of cells to perform specific functions with structural changes (1 mark). Dedifferentiation: differentiated cells regain division capacity (e.g., interfascicular cambium from parenchyma) (1 mark).
  5. It shows lag (slow), log/exponential (rapid) and stationary phases typical of living systems under natural conditions with limited nutrients (2 marks).
  6. Growth promoters (auxins, gibberellins, cytokinins) and growth inhibitors (ABA, ethylene) (1 mark each group + ½ mark each example).

Section C

  1. Meristematic phase: constantly dividing cells, rich protoplasm, thin cellulosic walls (1 mark). Elongation phase: vacuolation, cell enlargement, new wall deposition (1 mark). Maturation phase: maximal size, wall thickening, protoplasmic modifications (1 mark).
  2. Arithmetic: one daughter cell divides, linear curve, Lt = L0 + rt (1½ marks). Geometric: both daughters divide, S-curve, W1 = W0 ert (1½ marks).
  3. Plasticity: ability to follow different pathways forming different structures in response to environment/phases of life (1 mark). Juvenile vs mature leaves in cotton/coriander (heterophylly due to phase) (1 mark). Air vs water leaves in buttercup (environment) (1 mark).
  4. Discovery: Darwin’s phototropism experiment, isolated by Went from oat coleoptile tips (1 mark). Effects: apical dominance, parthenocarpy, prevent early fruit/leaf drop, induce rooting, xylem differentiation (any three — 2 marks).
  5. Ethylene: promotes ripening via respiratory climacteric, breaks dormancy, promotes abscission, root hair formation, flowering in mango/pineapple (any three effects — 3 marks).

Section D

  1. Sequence: cell division → expansion/elongation → differentiation/maturation → senescence/death (diagram description — 2 marks). Growth + differentiation = development (1 mark). Open differentiation: same meristem produces cells with different mature structures based on position (2 marks).
  2. Labelled sigmoid curve (lag, log/exponential, stationary phases — 2 marks). Explanation of phases (2 marks). Characteristic of living organisms due to limited nutrients leading to stationary phase (1 mark).
  3. Any three PGRs with three physiological effects each + one application (e.g., auxins: rooting, apical dominance, parthenocarpy — 5 marks with marking points).

Section E

Case 1

(i) Apical dominance; auxin (1 mark)
(ii) Gibberellins (GA3); terpenes (1 mark)
(iii) Increases stem length, yield by ~20 tonnes/acre (1 mark)
(iv) Intracellular (genetic) or intercellular chemical factors (PGRs) (1 mark)

Case 2

(i) Dedifferentiation (1 mark)
(ii) Redifferentiation (1 mark)
(iii) Cytokinins (kinetin) (1 mark)
(iv) Cells from same meristem attain different structures based on location (1 mark)

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All questions are answerable from the NCERT chapter text. Reviewed by GFIS faculty.