NEET Biology Plant Growth and Development Important Questions Set 01

These Class 11 NEET Biology important questions on Plant Growth and Development give 45 questions with step-by-step answers, arranged as very short, short and long answer types, as asked in school and board examinations. They help NEET aspirants revise the definitions, structures, differences and key terms of the chapter.

Very Short Answer Type Questions

Question 1. Give an example of growth in plants.

Answer:

(a) Expansion of leaves

(b) Increase in height of a stem of the plant. (Any 1)

Question 2. Which type of cells stop dividing and form permanent tissues?
Answer: Meristematic cells

Question 3. Name the phase of growth which occurs after meristematic phase of growth.
Answer: Elongation phase or phase of enlargement.

Question 4. W₁ = W₀ ert. What do W₀ and e stands for in the given expression?

Answer:

W₀ = initial size at the beginning of the growth.

e = base of natural logarithms.

Question 5. Define phytohormone.
Answer: It is defined as chemical substance other than nutrients which regulates one or more physiological activities at the same site where it is synthesized or away from the site of synthesis.

Question 6. A farmer wants to remove broad leaved weeds from his wheat field. Which plant hormone would you suggest to get the desired result?
Answer: Auxin i.e., 2, 4-D.

Question 7. Which phytohormone is responsible for synchronisation of flowering and fruit set in pineapple?
Answer: Ethylene

Question 8. Under severe drought condition, some plants close their stomata to reduce the loss of water. Name the phytohormone which is responsible for this action of plants.
Answer: ABA

Question 9. Some plants can flower only when they are exposed to low temperature for a few weeks. What do you call this phenomenon?
Answer: Vernalisation

Question 10. Which structures are formed from plumule and radicle?

Answer:

Plumule – Shoot system

Radicle – Root system

Short Answer Type Questions

Question 11. What is growth? Does swelling of raisins when kept in water constitutes the growth?

Answer:

Growth is an irreversible or permanent increase in size, volume and weight of an organ or its parts or even of an individual cell.

No, the swelling of raisins does not constitute the growth because it is a type of endosmosis which is reversible.

Question 12. Differentiate between primary growth and secondary growth.

Answer:

Question 13. Describe the following parameters of estimation of growth.
(a) Increase in cell size
(b) Increase in length

Answer:

(a) Increase in cell size : It can be used to measure or estimate the growth. For example, watermelon may increase in size by upto 3,50,000 times.

(b) Increase in length : The growth of a pollen tube is measured in terms of its length.

Question 14. Explain physiological differentiation with examples.

Answer:

Physiological differentiation means cells attain a particular function.

For example, absorption of water and minerals by root hairs, photosynthesis by mesophyll cells of leaves.

Question 15. Give two differences between arithmetic and geometric growth.

Answer:

Question 16. Which phase comes after lag phase of the sigmoid growth curve? Explain.
Answer: Log phase. In this phase, growth progresses rapidly or exponentially i.e., reaches to its maximum. Both the progeny cells obtained after mitotic cell division have the ability to divide continuously. During this phase maximum growth occurs.

Question 17. (a) What does 'r' indicate in the given expression? W₁ = W₀ ert
(b) Define efficiency index.

Answer:

(a) 'r' indicates the relative growth rate.

(b) It is the ability of the plant to produce new plant material.

Question 18. Why is water required for the proper growth of a plant?

Answer:

Because –

(i) It is responsible for cell elongation and maintenance of turgidity.

(ii) It provides the medium for enzymatic activities which are needed for growth.

Question 19. How is the tracheary element formed?
Answer: It is formed due to the elongation of cells which loose their protoplasm. A strong, elastic lignocellulosic secondary cell wall develops which does not allow tracheids to collapse under extreme tension.

Question 20. Expand IAA and NAA. Out of these two hormones, which one is natural?

Answer:

IAA – Indole-3-acetic acid

NAA – Naphthalene acetic acid

IAA is natural.

Question 21. (a) Where are auxins synthesised in plants?
(b) What happens to plants like lettuce when auxin is sprayed in high concentration?

Answer:

(a) Auxins are synthesised in growing apices of the stems and roots.

(b) Flowering is inhibited and it is advantageous in lettuce where only leaves are edible.

Question 22. Name the plant hormone which increases the stalk length in grapes. Also write the effect of this hormone on conifers and bolting.
Answer: Gibberellin. It causes early growth in conifers so that maturity is reached early in them. Gibberellin promotes internodal elongation prior to flowering in beet, cabbage and many plants with rosette habit.

Question 23. (a) Name two phytohormones which are responsible for cell division in callus.
(b) Which phytohormone is responsible for delaying the senescence and inhibition of apical dominance?

Answer:

(a) Cytokinin and auxin

(b) Cytokinin

Question 24. (a) What induces artificial ripening in fruits like tomato, mango and apple?
(b) Which is the only gaseous natural, plant growth regulator?

Answer:

(a) Ethylene

(b) Ethylene

Question 25. What names were given to the plant growth regulators that were discovered as inhibitors independently by three scientists? What are they all referred to as now?

Answer:

(i) Inhibitor B, Abscission II and dormin.

(ii) Now, they are referred as abscisic acid (ABA)

Question 26. Define development. Is appearance of chloroplasts in cells when exposed to sunlight, a development?

Answer:

(i) Development is the sequence of changes that an organism goes through during its life cycle from germination of the seed to senescence.

(ii) Yes

Question 27. (a) Give two examples of plants which show heterophyllous development?
(b) Which type of factors influence the developmental stages of a plant?

Answer:

(a) Cotton, coriander and larkspur. (Any two)

(b) Factors

Question 28. (a) What is the role of radicle in seed germination?
(b) Which structure shows active growth in bean seed after the elongation of radicle?

Answer:

(a) Radicle breaks the seed coat and passes downwardly in the soil to establish itself as the primary root.

(b) Hypocotyl shows growth

Question 29. Define the following :
(a) Photoperiod
(b) Photoperiodism

Answer:

(a) The length of light period is called photoperiod.

(b) The responses shown by the plants to changes in the relative lengths of dark and light period is called photoperiodism.

Question 30. (a) What happens to shoot apices before flowering?
(b) From which part of plant florigen migrates to shoot apices?

Answer:

(a) Shoot apices modify themselves into flowering apices.

(b) Leaves

Long Answer Type Questions

Question 31. Give a schematic diagram to show the various parameters used to estimate the growth of a plant.

Answer:

Question 32. Explain the phase of growth which occurs after the elongation phase.

Answer:

Maturation phase or phase of differentiation : The cells present just next to the cells of elongation phase represent the phase of differentiation. The enlarged cells develop into special or particular type of cells by undergoing structural and physiological differentiation.

After differentiation, the mature cells do not grow further and remain unchanged till death.

Question 33. (a) Which type of curve is obtained when size of a plant organ is plotted against time? Represent the curve graphically.
(b) Define relative growth rate.
Answer: (a) Sigmoid curve is obtained. Stationary phase organ e as the ph ntial of weight ne po Ex Size/ Lag phase Time
(b) Relative growth rate : The growth of the given system per unit time expressed on a common basis, e.g., per unit initial parameter is called the relative growth rate. Growth per unit time Relative growth rate = ×100 Initial size

Question 34. Calculate the relative growth rate :
(a) If 'A' leaf of 50 cm² grows 10 cm² per day and
(b) 'B' leaf of 20 cm² grows 10 cm² per day. Which leaf out of these two has low relative growth rate? Growth per unit time ×100
Answer: (a) RGR = Initial size 10 ×100 = 50 = 20% 10 ×100
(b) PGR = 20 = 50% 'A' leaf has low relative growth rate i.e., 20% compared to 'B' leaf i.e., having 50% relative growth rate.

Question 35. Write the name of phytohormone :
(a) Made up of terpene
(b) Which can fit in both categories : plant growth promoters and inhibitors
(c) Studied by Charles Darwin and his son
(d) Occurs in rapid cell division areas like root apices and young fruits
(e) Which is also known as antitranspirant?
Answer: (a) Gibberellic acid
(b) Ethylene
(c) Auxin
(d) Cytokinin
(e) ABA

Question 36. (a) Term auxin is derived from which Greek word?
(b) Explain how auxin was discovered?
Answer: (a) The word auxin is derived from greek word 'auxein' which means 'to grow'.
(b) Discovery : Auxin was the first hormone to be discovered. Charles Darwin and his son Francis Darwin observed that the stimulus of light was perceived by coleoptile tip of canary grass but the bending response to unilateral light as produced at a distance in growth zone i.e., subapical part. After a series of experiments conducted by other scientists, it was concluded that the sensation picked up by the coleoptile tip is transmitted to the subapical part which bends towards the direction of light. As it was found that :
(i) In an experiment if the coleoptile tip was removed then there was no bending of shoot towards light because the stimulus of light was not perceived.
(ii) When coleoptile tip was covered by an opaque tin foil cap, it could not perceive the stimulus of light and hence, no bending was observed. It was first extracted from human urine then went extracted it from oat.

Question 37. (a) What is the meaning of apical dominance?
(b) What happens when apical buds of tea plants are removed?
(c) What is the role of auxin in cell division?
(d) Which hormone can counteract apical dominance?
Mille

Answer:

(a) It is the phenomenon by which the presence of apical bud does not allow the nearby lateral or axillary buds to grow.

(b) When the apical bud of tea plants are removed, the lateral buds start developing into branches. It is done to produce more number of leaves so that yield can be increased.

(c) Auxin is responsible for initiation of promotion of cell division in cambium.

(d) Apical dominance is overcome by cytokinin.

Question 38. Explain the following
(a) Bolting
(b) Gibberellin stimulates seed germination
(c) Which is the most intensively studied form of GA?

Answer:

(a) Bolting : Gibberellins induce stem elongation in 'rossette plants' e.g., cabbage, beet. In rossette plants, internodal growth is retarded and leaves are developed profusely. In these plants, just prior to the reproductive phase, the internodes elongate enormously causing a marked increase in stem height. This is known as bolting.

(b) Gibberellins stimulate the synthesis of various types of hydrolytic enzymes for mobilisation of reserve food, e.g., amylases, proteases.

(c) The GA₃ is one of the first gibberellins to be discovered and remains the most intensively studied form.

Question 39. (a) Explain the discovery of cytokinin.
(b) Where is cytokinin found in plants?
(c) Which hormone in addition to cytokinin helps in cell division?

Answer:

(a) F. Skoog and his co-worker found that tobacco callus i.e., a mass of undifferentiated cells proliferated only when in addition with auxin, the culture medium is provided either with coconut milk or yeast extract of DNA.

Miller et al discovered the first cytokinin from degraded autoclaved herring sperm DNA which had a powerful cytokinesis (division of cytoplam) promoting effect. It is called kinetin (N⁶-furfurylamino purine). It is a synthetic product and not occur naturally in plants. Search for natural substances with cytokinin like activities led to the isolation of zeatin from corn kernels and coconut milk.

(b) It is found in root apices, developing shoot buds, young fruits

(c) Auxin

Question 40. (a) Where is ethylene synthesised in plants?
(b) Name the compound used as a source of ethylene.
(c) What happens to unripe fruits if ethylene is sprayed on them?
(d) How ethylene helps the plants to increase their absorption surface?

Answer:

(a) It is synthesised in almost all plant parts like roots, leaves, flowers, fruits, seeds etc. The maximum synthesis occurs during ripening of fruits and in the tissues undergoing senescence i.e., ageing.

(b) Ethephon

(c) They will ripe

(d) Ethylene promotes root growth and root hair formation.

Question 41. (a) Which hormone induces dormancy of seeds?
(b) What happens when a minute quantity of ABA is applied on leaves?
(c) Why ABA is known as inhibitor B?

Answer:

(a) ABA induces the dormancy of seeds.

(b) Application of minute quantity of ABA to leaves reduces transpiration to a great extent through partial closure of stomata. It thus, conserves water and reduces the requirement of irrigation. Thus, ABA increases the tolerance of plants to various kinds of stresses. Therefore, it is also called the stress hormone.

(c) ABA is known as inhibitor B because it acts as a general plant growth inhibitor and an inhibitor of plant metabolism.

Question 42. (a) How auxin and cytokinin work synergistically on cell division and antagonistically on apical dominance?
(b) Name two phytohormones which promote abscission of leaves, fruits and flowers.
(c) There are number of events in the life of a plant where more than one PGR interact to affect that event. Mention such four events.

Answer:

(a) Both auxin and cytokinin promote cell division. Auxin promotes the apical dominance whereas it is inhibited by cytokinin.

(b) Ethylene and ABA

(c) Dormancy in seeds/buds

Question 43. (a) What is the meaning of plasticity? Explain it with example.
(b) What are the essential requirements for breaking the dormancy of a seed?

Answer:

(a) The ability of plant to follow different pathways and produce different structures in response to environment. Example of plasticity is heterophylly. Heterophylly is the phenomenon of appearance of different forms of leaves on the same plant. It can be seen or observed in plants like cotton, coriander and larkspur. In such plants, the leaves of the juvenile plants are different in shape from those of mature plants.

(b) Water, oxygen and suitable temperature.

Question 44. Draw a well-labelled diagram to show the germination of seed.

Answer:

A well-labelled diagram should show these parts: Epicotyl hook; Seed coat; Epicotyl; Cotyledons; Soil line; Cotyledon; Hypocotyl.

Germination of seed.

Question 45. (a) What are day neutral plants? Give example.
(b) Which hormonal substance is responsible for flowering?
(c) Which parts of the plant perceive the stimulus of low temperature?
(d) What is the site of perception of light and dark duration for flowering?

Answer:

(a) Day neutral plants : These plants do not show any correlation between exposure to light duration and induction of flowering response. They can blossom throughout the year e.g., tomato, pepper, cucumber etc.

(b) Florigen is a hypothetical hormone which moves from leaves to shoot apex.

(c) Stem apex and embryo of the seed

(d) Leaves.