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Test: Plant Growth Regulators (Old NCERT) - NEET MCQ


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40 Questions MCQ Test - Test: Plant Growth Regulators (Old NCERT)

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Test: Plant Growth Regulators (Old NCERT) - Question 1

Match Column-I with Column-II and select the correct option from the codes given below

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 1

Charles Darwin and his son Francis Darwin (1880 are concerned with the discovery of auxins. They worker on Phalaris canarensis (Canary grass) and found tha the stimulus of unilateral illumination was picked up b; the coleoptile tip of canary grass, whereas a decapitate! coleoptile did not receive the stimulus.
Hori (1918) and Kurosawa (1926) are related to tfv discovery of gibberellins (gibberellic acid, GA).
The first cytokinin was discovered from degraded autoclave Herring sperm DNA by Miller etal, 1955. It is called kineti (6-furfuryl amino-purine). Kinetin does not occur naturall; It is a synthetic hormone. The first natural cytokinin Wc obtained from unripe maize grains or kernels by Letham i al (1964). It is known as zeatin (6-hydroxy 3-methyl trans 2 butenyl amono-purine). It also occurs in coconut milk.Coconut milk is arich source of cytokinin

Test: Plant Growth Regulators (Old NCERT) - Question 2

Who isolated auxins from tips of coleoptiles of oat seedlings?

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 2

Isolation of auxins from tips of coleoptiles of oat seedlings is based upon Avena coleoptile curvature test.
This experiment was devised by F.W Went (926). It is based on the quick polar transport of auxin, downwards in Avena coleoptile. The result will be differential growth and formation of curvature. Degree of curvature is almost proportional to the concentration of auxin.

Test: Plant Growth Regulators (Old NCERT) - Question 3

Match column I with column II and select the correct option from the codes given below.

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 3

Auxins can be natural or synthetic. Natural auxii are the auxins which occur naturally in plant parts, e. IAA (lndole-3-Acetic Acid). Related chemicals are indc 3-acetaldehyde, indole 3-acetonitrile, indole 3-butyric ac (IBA), etc. Synthetic auxins are the chemical substanc which have been artificially synthesized and cause vario physiological responses common to IAA. Some exampl of synthetic auxins are 2,4-D (2,4-dichlorophenoxy ace acid), 2,4,5-T (2,4,5-trichlorophenoxy acetic acid), α and β naphthalene acitic acid(NAA). IBA is considered as both natural and synthetic.

Test: Plant Growth Regulators (Old NCERT) - Question 4

Which of the following hormones is used in root formation on stem cutting?

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 4

Auxins stimulate root formation on the stem cuttings, e.g., IBA, IBA-alanine, NAA. NAA is synthetic auxin while IBA is considered as both natural and synthetic.

Test: Plant Growth Regulators (Old NCERT) - Question 5

Apical dominance in dicot plants is due to the presence of more_________ in the apical bud than in the lateral ones.

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 5

Apical dominance is the phenomenon by which presence of apical bud does not allow the nearby lateral buds to grow. When the apical bud is removed, the lateral buds sprout. Apical bud inhibits the growth of lateral buds by releasing auxins. When a plant is decapitated i.e., its apical bud is removed then the lateral buds sprout, resulting in dense bushy growth. This phenomenon is widely used in the tea plucking and hedge making.

Test: Plant Growth Regulators (Old NCERT) - Question 6

In addition to auxins, ................ must be supplied to the culture medium to obtain a good callus in plant tissue culture.

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 6

Callus is an unorganized, undifferentiated mass of diving cells formed during tissue culture which requires both auxins and cytokinins for its growth and differentiation. In callus, shoot regeneration is promoted by a cytokinin, such as BAP (Benzylaminopurine) and root regeneration is promoted by an auxin, such as NAA (Naphthalene acetic acid). Thus, shoot and root regenerations in callus are controlled by auxin-cytokinin balance. Usually, an excess of auxins promote root regeneration and that of cytokinins promote shoot regeneration.

Test: Plant Growth Regulators (Old NCERT) - Question 7

Select the mismatched pair.

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 7

Gibberellic acid increases the yield of sugarcane crop. Cytokinins inhibit apical dominance and act antagonistically to auxins which promote apical dominance. Rhizomes, corms, tubers, seeds (e.g. peanut) and other storage organs can be made to sprout early by exposing them to ethylene. Abscisic acid is a plant growth inhibitor, which inhibits seed germination.

Test: Plant Growth Regulators (Old NCERT) - Question 8

Read the given statements and select the correct option.
(i) Darwin and Darwin (1880) found that sensation of unilateral illumination was perceived by the coleoptile tip of canary grass.
(ii) IAA is universal natural auxin, discovered by Kogl et al.
(iii) IBA is both natural and synthetic auxin.
(iv) Auxins promote the growth of lateral shoots.

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 8

Auxins promote the growth of apical buds and suppress the growth of lateral buds/lateral shoots.

So the correct option is 'Statements (i), (ii) and (iii) are correct.'

Test: Plant Growth Regulators (Old NCERT) - Question 9

 The term 'auxin precursor' refers to _________________.

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 9

The raw material which is used in synthesis of auxin is called auxin precursor. It is tryptophan of IAA.

Test: Plant Growth Regulators (Old NCERT) - Question 10

Functions of auxins include

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 10

NA A and 2,4-D are often employed for inducing flowering in litchi and pineapple. Application of auxins (e.g., IA A, IBA) and conjugate auxins (e.g., IBA-alanine) to unpollinated pistils make them develop into seedles fruits (or parthenocarps) which carry a better market price than the normal fruits having seeds. 2,4-D and 2,4,5-T are used as weedicides (herbicides) which destroy broad leaved weeds in cereal crops and lawns. Dalapon (2,2-dichloropropionic acid) Kills grasses in broad leaved crops.

Test: Plant Growth Regulators (Old NCERT) - Question 11

The hormone responsible for apical dominance is

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 11

Auxins are mainly responsible for apical dominance. IAA is a natural auxin.

Test: Plant Growth Regulators (Old NCERT) - Question 12

The term 'antiauxin' refers to

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 12

The compounds which inhibit the action of auxins are called as antiauxins, e.g. p-chlorophenoxy isobutyric acid (PCIB)

Test: Plant Growth Regulators (Old NCERT) - Question 13

Which of the following effects of auxins on plants is the basis for their commercial application?

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 13

Auxins are used for inducing root formation in stem cuttings in many commercially important vegetatively propagated plants, and also plants propagated through layering. 
Example- Rose, guava, Ficus etc
Here, synthetic Auxin like NAA (Naphthalene Acetic Acid) is used.

Test: Plant Growth Regulators (Old NCERT) - Question 14

The phenomenon of apical dominace can be overcome by exogenous application of

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 14

Presence of cytokinin in an area caues preferetial movement of nutrients towards it. When applied to lateral buds, they help in their growth despite the presence of apical bub. They thus act antagonistically to auxin which promotes apical dominance. Therefore, cytokinin can overcome apical dominance, caused by auxins.

Test: Plant Growth Regulators (Old NCERT) - Question 15

A plant hormone that induces morphogenesis in plant tissue culture is

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 15

Cytokinins play a vital role in morphogenesis in plants. It opposes initiation of roots in stem cuttings treated with auxin and results in the formation of callus at the cut end. It is now well known that kinetin-auxin interaction controls the momhogenetic differentiation of shoot and root meristems.

Test: Plant Growth Regulators (Old NCERT) - Question 16

Induction of cell division activity and delay in senescence is caused by

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 16

The most important function of cytokinins is the promotion of cell division. The varying amounts of cytokinins, alongwith sufficient auxins is required for the growth of callus in tissue culture experiments. Cytokinins delay the senescence of leaves and other organs by mobilisation of nutrients. it is known as Richmond-Lang effect.

Test: Plant Growth Regulators (Old NCERT) - Question 17

Cytokinins are mostly

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 17

Cytokinins are plant growth hormones which are basic in nature, cytokinsis (=cell division) either alone or in conjunction with auxin. Kinetin, a synthetic cytokinin, is 6-furfuryl amino purine. Zeatin, a natural cytokinin, is 6-hydroxy 3-methyl trans 2-butenyl amino purine.

Test: Plant Growth Regulators (Old NCERT) - Question 18

The hormone which reduces transpiration rate by inducing stomatal closure is

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 18

ABA (Absisic acid) is a stress hormone which is synthesised by the plant during drought or other stress conditions. It causes rapid movement of K+ ions out of the transpiration rate.

Test: Plant Growth Regulators (Old NCERT) - Question 19

High concentration of auxin is present in

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 19

The term 'auxin' is applied to the indole-3-acetic acid (IA A) and to other natural and synthetic compounds having certain growth regulating properties. They are generally produced by the growing apices of the stem, from where they migrate to the regions of their action.

Test: Plant Growth Regulators (Old NCERT) - Question 20

The activity of α - amylase in the endosperm of a germinating seed of barley is induced by

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 20

Gibberellic acid induces de novo (a new) synthesis of various hydrolytic enzymes, such as, α-amylase, ribonuclease, α-1,3-glucanase and protease in aleurone cells of barley grains. This has been experimentally shown by isolating the aleurone layer and treating it with gibberellin solution. These enzymes are mobilised to endosperm during germination and hydrolyse the storage reserve.

Test: Plant Growth Regulators (Old NCERT) - Question 21

Hormone involved in phototropism is

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 21

Phototropic curvature is the result of uneven distribution of auxin. Darwin and Darwin observed that the coleoptiles of canary grass responded to unilateral illumination by growing towads the light source (phototropism). After a series of experiments, it was concluded that the tip of coleoptile contains auxin that caused the bending of the entire coleoptile in relation to the direction of light.

Test: Plant Growth Regulators (Old NCERT) - Question 22

Which of the following physiological effects is caused in plants by gibberellic acid?

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 22

One of the most striking effects of the gibberellins is the reversal of dwarfism in many genetically dwarf plants. Rosette plant of sugar beet, when treated with GA3, undergoes marked longitudinal growth of axis. Similarly, dwarf pea and dwarf corn attain almost normal size when treated with gibberellins. The dwarf plants have very low GA level which appears to account for the dwarfing habit. Thus, the external supply of GA to such plants causes rapid elongation.

Test: Plant Growth Regulators (Old NCERT) - Question 23

Gibberellin was first extracted from _____________.

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 23

In Japan (in early 1800's), certain rice plants suffers from bakanae (foolish seedling) disease. Such rice plants were thin, pale green, spindle shaped, longer by 50% than the healthy plants, and were sterile. The disease was found by Hori and Kurosawa to be caused by a fungus. Gibberella fujikori. The fungus is the perfect stage of Fusarium moniliforme.

Test: Plant Growth Regulators (Old NCERT) - Question 24

Hormone responsible for ageing is

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 24

ABA is a plant growth inhibitor. It promotes senescence and ageing in plant parts.

Test: Plant Growth Regulators (Old NCERT) - Question 25

Bud dormancy is induced by

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 25

ABA is known as dormin as it induces dormancy in buds, underground stems and seeds in a variety of plants. e.g., ABA induces winter bud dormancy in duckweed plant.

Test: Plant Growth Regulators (Old NCERT) - Question 26

Internodal elongation is stimulated by

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 26

Gibberellins specifically induce internodal elongation in genetically dwarf verieties of plants like pea and maize.

Test: Plant Growth Regulators (Old NCERT) - Question 27

Removal of auxin source demonstrates that leaf abscission is _______by auxin, and apical dominance is________by auxin.

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 27

Shedding of mature leaves from the stem or ripe furits from the stem is called abscission. Generally a layer of tissue is formed at the base of the organ. This layer of tissue is called abscission zone. Abscission zone does not occur when the concentration of auxin is high, particularly when the gradient of auxin is steep, i.e, more auxin on distal side and less auxin on proximal side. the abscission zone formation occus rapidly when the auxin gradient become slight or netural. Moreover, the plant hormone ethylene is found to promote the abscission. Thus, a high concentration of auxin prevents the formation of abscission layer and the phenomenon is controlled by the concentrations of auxin and ethylene. Apical dominance is promoted by auxin.

Test: Plant Growth Regulators (Old NCERT) - Question 28

The fruits can be left on the three longer using GA so as to extend the market period. This is due to which function of GA?

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 28

Some of the gibberellins are commercially used in the delayed ripening of fruits. GA; delays senescence so thal fruit can be left on the tree for longer period. It extendi period of marketing. Ripening of Citrus fruits can be delayed with the help of gibberellins. This is useful in storing the fruits.

Test: Plant Growth Regulators (Old NCERT) - Question 29

Natural cytokinins are synthesised in regions where rapid cell division occurs. Such regions are

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 29

About 18 types of cytokinins have been discovered till now. Some of them are constituents of tRNAs. Roots are considered as the major source of cytokinin synthesis, from roots, the cytokinins pass upwardly through xylem. Cytokinin synthesis also occurs in the areas where cell divisions takes place e.g., growing embryos and developing seeds, endosperm of seeds, young fruits, develpoing shoot buds, etc.

Test: Plant Growth Regulators (Old NCERT) - Question 30

Cytokinins help to produce all except

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 30

Rooting on cut stem is a function of auxin not cytokinin.

Test: Plant Growth Regulators (Old NCERT) - Question 31

Seed dormancy is caused by

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 31

Seed dormancy is mainly caused by ABA. Dormancy allows seeds to tolerate desiccation and extremes of temperature better. Due to its action of inducing dormancy in seeds, buds etc. ABA is also called as dormin.

Test: Plant Growth Regulators (Old NCERT) - Question 32

Read the given statements and select the option that correctly identifies the incorrect ones.
(i) Cytokinin is primarily concerned with cell division.
(ii) C2H4 breaks seed and bud dormancy
(iii) ABA stimulates the opening of stomata.
(iv) C2H4 initiates germination in peanut seeds, sprouting of potato tubers.
(v) ABA is synergistic to GA.

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 32

ABA caues stomatal closure. ABA is antagonistic to GA.

Test: Plant Growth Regulators (Old NCERT) - Question 33

The most widely used compound as a source of C2H4 is

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 33

Ethephon, 2-chloroethyl phosphonic acid (Ethrel) is a source of ethylene used commercially. It is used in aqueous solution and relkeases ethylene slowly.

Test: Plant Growth Regulators (Old NCERT) - Question 34

Which of the following statements regarding gibberellins is incorrect?

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 34

Gibberellins are weakly acidic growth hormones having gibbane ring structure which cause cell elongation of intact plants in general and increased the internodal length of genetically dwarfed plants (e.g., pea, corn), in particular. 
GA3 was one of the first gibberellins to be discovered and remains the most intensively studied form. 
The major sites of gibberellin production in plants we embryos, roots and young leaves near the shoot tip.

Test: Plant Growth Regulators (Old NCERT) - Question 35

Which among the following is not a function of cytokinis?

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 35

Cytokinins do not take part in fruit ripening. Ethylene hormone stimulates ripening of fruits.

Test: Plant Growth Regulators (Old NCERT) - Question 36

Gibberellins promote the formation of ______(A)flowers on genetically ______(B) plants in Cannabis whereas ethylene promotes formation of ______(C) flowers on genetically _____(D) Cannabis plants.

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 36

Gibberellins promote the formation of male flowers on genetically female plants in Cannabis whereas ethylene promotes formation of female flowers on genetically male plants. - Example, Cucurbits

Test: Plant Growth Regulators (Old NCERT) - Question 37

A farmer grows cucumber plants in his field. He wants to increase the number of female flowers in them. Which plant growth regulator can be applied to achieve this?

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 37

Gibberillins and ethylene control sex expression in some plants. Gibberellins promote the formation male flowers on genetically female plants of Cannabis can also replace female flowers with male flower or monoecious plants of cucurbits. Like auxins and cytokinins ethylene has a feminising effect on sex expression. They genetically male plants of Cannabis can be induced to produce female flowers in the presence of ethylene. The number of female flowers and hence fruit is enhanced monocious plant like cucumber.

Test: Plant Growth Regulators (Old NCERT) - Question 38

If a rotten fruit gets mixed with unripe fruits, the unripe fruits will

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 38

Ethylene production by plants is autocatalytic,i.e. a small amount of ethylene will stimulate production of its larger amounts. Thus, a few ripe fruits will initiare ripening of nearby fruits. It is, therefore, a common practice to keep few ripe bananas with unripe bananas to hasten ripening.

Test: Plant Growth Regulators (Old NCERT) - Question 39

What would happen if you forget to add cytokinin to the culture medium?

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 39

Cytokinin is a plant growth hormone that promotes cell division or cytokinesis in the roots and shoots of the plants. In plant tissue culture, ratio of auxin and cytokinin affects root and shoot formation. If auxin is more then root formation is promoted whereas if cytokinin is more then shoot formation is promoted. 
Hence, if we forget to add cytokinin to the culture medium then callus will not develop shoot buds.

Test: Plant Growth Regulators (Old NCERT) - Question 40

Read the given statements and select the correct option.
Statement 1: Ethylene is a gaseous hormone.
Statement 2: Ethylene causes climacteric ripening of fruits.

Detailed Solution for Test: Plant Growth Regulators (Old NCERT) - Question 40

Ethylene is a gaseous hormone. It aids in ripening of climacteric fruits and dehiscence of dry fruits. Climacteric fruits are the fleshy fruits which show a sudden sharp rise of respiration rate at the time of ripening (respiratory climacteric). They are usually transported is green or unripe stage. Ethylene is used to induce artificial ripening of these fruits e.g., Apple Mango, Banana, etc.

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