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Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Cytokinins are mostly ____________.

  1. glucosides

  2. phenolics

  3. amino purines

  4. organic acids.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cytokinins are plant growth hormones which are basic in nature, either amino purine or phenyl urea derivatives, that promote cytokinesis (= 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.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Select the pair that consists of plant growth promoters only.

  1. Auxins and cytokinins

  2. Gibberellins and ABA

  3. Ethylene and ABA

  4. All of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Auxins and cytokinins are plant growth promoters, the roles played by auxin and cytokinin are as follows.

Auxins: Cell enlargement and longitudinal growth of root and shoot.
             Reactivation of cambium in the growth season, that is, responsible for secondary growth, promotes apical dominance and parthenocarpy, inhibits abcission.
Cytokinins: induces morphogenesis that is differentiation of cells into tissues and organs.delays senescence, breaks dormancy and promotes seed germination, enhances expression of a sexual characteristic- femaleness in some plants.
Auxin/cytokinin ratio influences root and shoot formation and growth
So, the correct answer is 'Auxins and cytokinins'

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Which among the following is not a function of cytokinins?

  1. Essential for Cytokinesis during cell division

  2. Delays the senescence of leaves

  3. Helps in fruit ripening

  4. Helps to overcome apical dominance
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Fruit ripening or climacteric fruit ripening is induced by ethylene in most of the fruits, and therefore is not a function of cytokinins.

So, the correct answer is 'Helps in fruit ripening'

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

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

  1. Root apices

  2. Developing shoot buds

  3. Young fruits

  4. All of these.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
About 18 types of cytokinins have been discovered till now. Some of them are constituents of t RNAs. Roots are considered as the major source of cytokinin synthesis; from roots, the cytokinins pass upwardly through the xylem. Cytokinin synthesis also occurs in the areas where cell division takes place e.g., growing embryos and developing seeds, endosperm of seeds, young fruits, developing shoot buds, etc.
So the correct option is 'All of these'.
Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

A plant hormone used for Inducing morphogenesis in plant tissue culture is ______________.

  1. abscisic acid

  2. gibberellin

  3. cytokinin

  4. ethylene.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

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.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

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

  1. ABA

  2. Cytokinins

  3. Gibberellins

  4. Ethylene
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
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.
So the correct answer is 'cytokinins'.
Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Cytokinins help to produce all except

  1. New leaves

  2. Chloroplast in leaves

  3. Lateral shoot growth and adventitious shoot formation

  4. Rooting on cut stem
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Rooting of cut stem is induced by spraying synthetic auxins like NaphthaleneAceticAcid and not cytokinins, in plants that are vegetatively propagated by stem cuttings.

So, the correct answer is 'Rooting on cut stem'

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

First natural cytokinin was discovered by

  1. Skoog and Miller

  2. Letham

  3. Benson and Calvin

  4. Thimann and Went
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The first cytokinin was isolated from herring sperm in 1955 by Miller and his associates . This compound was named kinetin because of its ability to promote cytokinesis. Hall and deRopp reported that kinetin could be formed from DNA degradation products in 1955. The first naturally occurring cytokinin was isolated from corn in 1961 by Miller. It was later called zeatin. 

Therefore, the correct answer is option A.