CBSE Class 11 Biology HOTs Plant Growth and Development

Plant Growth and Development

MCQ Questions for NCERT Class 11 Biology Plant Growth and Development

Question. Ethylene is not directly applied in the field as a gas due to its high diffusion rate. Which compound is used to overcome this limitation?
(a) Ethephon
(b) Agent orange
(c) Benzaldehyde
(d) 2,4,5-T

Answer : A

Question. Which of the following plant hormone is not a growth inhibitor?
(a) IAA
(b) Dormin
(c) ABA
(d) Ethylene

Answer : A

Question. Which hormone plays important role in phototropism?
(a) Gibberellin
(b) Auxins
(c) Ethylene
(d) Cytokinin

Answer : B

Question. Phytohormone A causes apical dominance while phytohormone B overcomes the same.
Select the option that correctly identifies A and B.
           A                  B
(a) Auxin            Cytokinin
(b) Cytokinin         Auxin
(c) Gibberellin     Cytokinin
(d) Auxin            Gibberellin

Answer : A

Question. Consider the following statements regarding phytohormones.
I. The genetically male plants of Cannabis can be induced to promote female flowers in response to ethylene.
II. Auxins and gibberellins control xylem differentiation.
III. IBA reduces sweetening of fruits.
IV. Auxins delays abcission of older leaves and fruits.
The incorrect statements are
(a) I, II and III
(b) I, III and IV
(c) II and IV
(d) I and IV.

Answer : B

Question. Which of the following acids is a derivative of terpenes?
(a) Indole acetic acid
(b) Naphthalene acetic acid
(c) Abscisic acid
(d) Gibberellic acid

Answer : D

Question. In 1926, the Japanese biologist Eiichi Kurosawa showed that the bakanae (“foolish seedling”) disease of rice was caused by a substance produced by the fungus Gibberella fujikuroi. The substance was named gibberellin and was shown to cause elongation of stem tissues. Which of the following statements about gibberellin is false?
(a) Pea plants carrying the dwarf mutation would be expected to have higher levels of gibberellin in their stems than normalplants. 
(b) If gibberellin is applied to the stems of dwarf pea plants, the stems elongate so that plant reach normal height.
(c) Dwarf pea plants have a mutation in the gibberellin biosynthetic pathway.
(d) Normal pea plants respond to gibberellin by growing even taller.

Answer : A

Question. Read the given statements and identify the PGRs X, Y and Z.
(i) X induces accumulation of salts inside the cells.
(ii) Y promotes rapid elongation of leaf bases and internodes in deep water rice plants.
(iii) Application of Z to leaves shall reduce transpiration.
(a) X-Auxin, Y-Cytokinin, Z-Ethylene
(b) X-Cytokinin, Y-Ethylene, Z-ABA
(c) X-Auxin, Y-Cytokinin, Z-ABA
(d) X-Cytokinin, Y-ABA, Z-Ethylene

Answer : B 

Question. Consider the following statements about phytohormones and identify them as true or false.
A. Natural auxin promotes flowering in plants which require vernalisation.
B. Ethylene decreases sensitivity to gravity.
C. Like gibberellins, abscisic acid promotesa mylase formation during seed germination.
D. Young fruit thinning done by ethylene in walnut allow better growth of remaining fruits.
E. Gibberellins have no role in apical dominance.
Choose the correct option.
     A B C D E
(a) F T F F T
(b) F T F T F
(c) T T F T T
(d) F T F T T

Answer : D

Question. A young dicot seedling (e.g., soybean) is laid horizontally on a surface and is subjected to gravity stimulus. The shoot bends in upward direction and the root bends in downward direction. Which out of the following is the possible reason for this movement?
(a) Redistribution of auxins throughout the seedlings is responsible for the stimulatory unequal growth in shoots and roots.
(b) Redistribution of cytokinins throughout the seedlings is responsible for the stimulatory unequal growth in roots and shoots.
(c) Redistribution of auxins in roots and cytokinins in shoots is responsible for stimulatory unequal growth.
(d) Redistribution of auxins in shoots and cytokininis in roots is responsible for stimulatory unequal growth.

Answer : A

Question. Match the following columns and select the correct option.
        Column I               Column II
A. Human urine             (i) Cytokinin
B. Gibberella fujikuroi    (ii) Auxin
C. Herring sperm DNA   (iii) Ethylene
D. Ripening of fruit        (iv) ABA
E. Aging leaves of plants (v) GA
(a) A - (ii), B - (iii), C - (iv), D - (v), E - (i)
(b) A - (ii), B - (v), C - (i), D - (iii), E - (iv)
(c) A - (i), B - (ii), C - (iii), D - (iv), E - (v)
(d) A - (v), B - (iv), C - (iii), D - (ii), E - (i)

Answer : B

Question. Refer the functions of the growth hormones given below.
I. Cell division II. Cell enlargement
III. Pattern formation IV. Tropic growth
V. Flowering VI. Fruiting
VII. Seed germination VIII. Response to wound
IX. Response to stresses of biotic and abiotic origin
Identify the functions of growth promoters and growth inhibitors from the above.
Functions of Functions of growth promoters growth inhibitors
(a) I, II, VII, IX III, IV, V, VI, VII
(b) VIII, IX I, II, III, IV, V, VI, VII
(c) I, II, III, IV, V, VI, VII VIII, IX
(d) I, II, III, IV, V, VI, VII, IX VIII

Answer : C

Question. Read the following statement (i-iv) regarding “ethephon” and answer the question which follows them.
(i) Ethephon is sprayed in aqueous solution and is readily absorbed and transported within the plant.
(ii) It hastens fruit ripening in tomatoes and apples.
(iii) It can be used to induce fruit thinning in cotton, cherry and walnut.
(iv) It is used to promote female sex expression in cucumber and increase yield.
How many of the above statement (s) is/are correct?
(a) One
(b) Two
(c) Three
(d) All of these

Answer : D

Ques. The process of growth is maximum during
(a) log phase
(b) lag phase
(c) senescence
(d) dormancy.

Answer: A

Ques. Typical growth curve in plants is
(a) stair-steps shaped
(b) parabolic
(c) sigmoid
(d) linear. 

Answer: C

Ques. Senescence as an active developmental cellular process in the growth and functioning of a flowering plant, is indicated in
(a) annual plants
(b) floral parts
(c) vessels and tracheid differentiation
(d) leaf abscission.

Answer: C

Ques. Name the plant growth regulator which upon spraying on sugarcane crop, increases the length of stem, thus increasing the yield of sugarcane crop.
(a) Cytokinin
(b) Gibberellin
(c) Ethylene
(d) Abscisic acid

Answer: B

Ques. Which of the following is not an inhibitory substance governing seed dormancy?
(a) Gibberellic acid
(b) Abscisic acid
(c) Phenolic acid
(d) Para-ascorbic acid

Answer: A

Ques. It takes very long time for pineapple plants to produce flowers. Which combination of hormones can be applied to artificially induce flowering in pineapple plants throughout the year to increase yield?
(a) Cytokinin and Abscisic acid
(b) Auxin and Ethylene
(c) Gibberellin and Cytokinin
(d) Gibberellin and Abscisic acid 

Answer: B

Ques. Fruit and leaf drop at early stages can be prevented by the application of
(a) ethylene
(b) auxins
(c) gibberellic acid
(d) cytokinins.

Answer: B

Ques. You are given a tissue with its potential for differentiation in an artificial culture. Which of the following pairs of hormones would you add to the medium to secure shoots as well as roots?
(a) IAA and gibberellin
(b) Auxin and cytokinin
(c) Auxin and abscisic acid
(d) Gibberellin and abscisic acid 

Answer: B

Ques. The Avena curvature is used for bioassay of
(a) IAA
(b) ethylene
(c) ABA
(d) GA3.

Answer: A

Ques. Auxin can be bioassayed by
(a) potometer
(b) lettuce hypocotyl elongation
(c) Avena coleoptile curvature
(d) hydroponics. 

Answer: C

Ques. What causes a green plant exposed to the light, on only one side, to bend towards the source of light as it grows?
(a) Light stimulates plant cells on the lighted side to grow faster.
(b) Auxin accumulates on the shaded side, stimulating greater cell elongation there.
(c) Green plants need light to perform photosynthesis.
(d) Green plants seek light because they are phototropic. 

Answer: B

Ques. Dr. F. Went noted that if coleoptile tips were removed and placed on agar for one hour, the agar would produce a bending when placed on one side of freshly-cut coleoptile stumps. Of what significance is this experiment?
(a) It made possible the isolation and exact identification of auxin.
(b) It is the basis for quantitative determination of small amounts of growth-promoting substances.
(c) It supports the hypothesis that IAA is auxin.
(d) It demonstrated polar movement of auxins. 

Answer: A

Ques. Which one of the following growth regulators is known as ‘stress hormone’?
(a) Abscisic acid
(b) Ethylene
(c) GA3
(d) Indole acetic acid

Answer: A

Ques. During seed germination, its stored food is mobilized by
(a) ABA
(b) gibberellin
(c) ethylene
(d) cytokinin.

Answer: B

Ques. The pineapple which under natural condition is difficult to blossom has been made to produce fruits throughout the year by application of
(a) NAA, 2, 4-D
(b) Phenyl acetic acid
(c) Cytokinin
(d) IAA, IBA.

Answer: A

Ques. Through their effects on plant growth regulators, what do the temperature and light control in the plants?
(a) Apical dominance
(b) Flowering
(c) Closure of stomata
(d) Fruit elongation 

Answer: B

Ques. Which one of the following generally acts as an antagonist to gibberellins?
(a) Zeatin
(b) Ethylene
(c) ABA
(d) IAA 

Answer: C

Ques. Phototropic curvature is the result of uneven distribution of
(a) gibberellin
(b) phytochrome
(c) cytokinins
(d) auxin.

Answer: D

Assertion & Reasoning Based MCQs

For question numbers 51-57, two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion. (c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.

Question. Assertion : Axillary buds in actively growing herbaceous plants generally remain dormant.
Reason : This is due to apical dominance which is under the influence of auxins.

Answer : A

Question. Assertion : Cytokinins increases shelf life of fruits and vegetables.
Reason : Cytokinins induce cell division.

Answer : B

Question. Assertion : Plant growth regulators (PGRs) are very important for plant growth and development.
Reason : Auxins do not induce flowering in gymnosperms.

Answer : B

Important Questions for NCERT Class 11 Biology Plant Growth and Development

Short Answer Type Questions

Question. List five main groups of natural, plant growth regulators. Write a note on discovery, physiological functions and agricultural/ horticultural applications of any one of them. 

Answer. Five main groups of natural, plant growth regulators are auxins, gibberellins, ethylene, cytokinins and ABA. Auxins
(i) Discovery – Auxins was first isolated from human urine. They are generally produced by the growing apices of the stems and roots. Auxins like IAA and IBA have been isolated from plants. NAA (Naphthalene Acetic acid) and 2, 4-D (2, 4-dichlorophenoxyacetic) are synthetic auxins.
(ii) Physiological functions – They help to initiate rooting in stem cuttings, an application widely used for plant propagation. Auxins promote flowering, i.e., in pineapples. They help to prevent fruit and leaf drop at early stages but promote the abscission of older mature leaves and fruits. (iii) Agricultural/horticultural applications – Auxins also induce parthenocary, e.g., in tomatoes. They are widely used herbicides 2, 4-D, and are used to kill dicotyledonous seeds. They do not effect mature monocotyledonous plants, instead is used to prepare seed-free lawns by gardeners. It also controls xylem different and helps in cell division.

Question. The role of ethylene and abscisic acid is both positive and negative. Justify the statement.

Answer. The role of ethylene and abscisic acid is both positive and negative. Ethylene is a simple gaseous PGR. As a negative effect, it is synthesised in large amount by tissues undergoing senescence and ripening. It also promotes senescence and abscission of plant organs expecially of leaves and flowers. As a positive effects, ethylene breaks seed and bud dormancy, initiates germination in peanut seeds, sprouting of potato tubers. It promotes internode/petiole elongation in deep water rice plants. It helps leaves/inner parts of the shoot to remain above water.

Question. How are gibberellins useful in agriculture to improve productivity. Give any three points in support of your answer.

Answer. Gibberellins are useful in agriculture in the following ways
(i) Application of gibberellins increase the length of the stem and increase the yield of sugar in sugarcane.
(ii) Gibberellins delay senescence and the fruits can be left on the trees for longer duration, so as to increase the market period.
(iii) It can cause fruit like apple to elongate and improve in shape.

Question. Name the categories of plant hormones concerned with each of the following and describe one other function of each of the three categories of plant hormones
(i) Inhibition of seed germination
(ii) Promote flowering
(iii) Cell division-promoting activity.

Answer. (i) Abscisic acid, signals closure of stomata to prevent water loss during water stress.
(ii) Auxins, controls cell division and xylem differentiation.
(iii) Cytokinin, helps in the growth of lateral buds and overcome apical dominance.

Question. Mention one antagonistic function for each of the given pair of hormones.
(a) Gibberellin - Auxin
(b) Cytokinin - Abcisic acid
(c) Auxin - Cytokinin

Answer. (a) Gibberellin induces formation of male flowers (masculinity) while auxin induces production of female flowers (feminism) in plants.
(b) Cytokinins prevent senescence and induces stomatal opening but abscisic acid induces senescence and brings about closure of stomata.
(c) Auxin causes apical dominance while it is overcome by cytokinin.

Question. Name a plant hormone that can never act alone. List any three activities of this hormone in conjunction with auxins.

Answer. Cytokinins can never act alone. The three activities of cytokinins in conjunction with auxins :
(a) Morphogenesis : Both auxin and cytokinin should be proportionate in order to allow shoot and root development. If both these PGRS are present in roughly equal concentrations, callus or undifferentiated tissue will be formed. If auxin is higher than cytokinin, then roots will form while if cytokinin is higher than auxin, shoots will form. Thus, auxin and cytokinin have antagonistic effects. This phenomenon is called morphogenesis and is applied to produce a large number of plants by a technique called micropropagation.
(b) Apical dominance : Cytokinins have also known to antagonize auxins in apical dominance. It has been found that if the internal levels of cytokinins in the plant body are high, they promote growth of axillary buds, thereby reducing or overcoming apical dominance.
(c) Cell division : Cytokinins have a direct role in regulating progression through the cell cycle and promote cell division in tissue culture provided auxins are present. Cell division in callus also requires both the hormones.

Question. What would be expected to happen if :
(a) GA3 is applied to rice seedlings
(b) dividing cells stop differentiating
(c) a rotten fruit gets mixed with unripe fruits
(d) you forget to add cytokinin to the culture medium.

Answer. (a) The coleoptile will elongate rapidly, as GA3 helps in cell growth.
(b) The development of callus (mass of undifferentiated cells) will take place.
(c) The unripe fruits will ripe quickly because of the increased rate of respiration due to emission of ethylene from rotten fruit. (d) Cell division will retard and shoot will not initiate from the callus.

Question. What is bolting? How can it be artificially induced?

Answer. It is a process of rapid stem elongation, generally in rosette plants and usually precedes flowering. In general, environmental factors such as photoperiod and/or low temperature trigger bolting in these plants. Exogenous application of gibberellins has been found to induce bolting and flowering in these plants in the absence of required environmental conditions.

 Long Answer Type Questions

Question. Which hormone prevents senescence? Write its different functions and uses.

Answer. Cytokinins cause delay in senescence of intact plant parts. The various functions of cytokinins are as follows :
(i) They promote cell division in tissue culture provide auxins are present. They have a direct role in regulating progression through the cell cycle. Both auxin and cytokinin should be proportionate in order to allow shoot and root development.
(ii) If the internal leaves or cytokinins in the plant body are high, they promote growth of axillary buds, thereby reducing or over coming apical dominance. If cytokinins are applied to axillary buds, lateral shoot growth is promoted.
(iii) They also aid in formation of new leaves, chloroplast development, formation of lateral and adventitious shoots, etc.
(iv) Cytokinins have been found to cause a delay in sentence in mature leaves probably by directing nutrient mobilization and retention by stimulating metabolic activities.
(v) They promote femaleness in plants like auxins and ethylene and help in induction of parthenocarpy. Uses of cytokinins :
(i) In tissue culture, to form new plant varieties by morphogenesis.
(ii) To prolong the shelf-lives of vegetables such as cabbage, lettuce, etc.
(iii) Keep cut flowers fresh.
(iv) To help the plant develop resistance to certain pathogens and extreme temperature variations.

Question. What are plant growth regulators? Name any for different chemical nature of them with one example of each.

Answer. Plant growth regulators are small, simple molecules secreted in minute quantities, that influence various physiological functions in plants. They are of diverse chemical composition. (i) Indole compounds [such as-indole-3-acetic acid (IAA)]
(ii) Adenine derivatives [such as kinetin, 6-furfuryl amino purnie]
(iii) Derivatives of carotenoids [such as abscisic acid (ABA)]
(iv) Terpenes [such as gibberellic acids]