Biology

Plant Growth and Hormones

695 Questions

Plant growth and hormones is a vital topic in biology that covers the physiological effects of different plant regulators like auxins, gibberellins, and cytokinins. These concepts are frequently tested in various general science sections of competitive exams. Practicing these questions helps clarify complex mechanisms like vernalisation, senescence, and tropism for test takers.

Abscisic acid effectsCytokinin functionsAuxins and tropismPlant tissue cultureSenescence in plantsNatural plant hormones

Plant Growth and Hormones Questions

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

Pruning of plants promotes branching, because the axillary buds get sensitized to

  1. Ethylene

  2. Gibberellin

  3. Cytokinin

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

Cytokinin are a class of plant growth substance that promote cell division or cytokinesis in plant roots and shoots. They are involved primarily in cell growth and differentiation but also affects apical dominance, axillary bud growth and leaf sensecence. Pruning of plants promote branching because the axillary buds get sensitized to cytokinin.

Therefore, the correct answer is option C.

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

Coconut water is rich in 

  1. Auxins

  2. Gibberellin

  3. Abscisic acid

  4. Cytokinin
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Cytokinins stimulate cell division, even in non-meristematic cells, in presence of auxin. They are most abundant in the growing tissues which are active site of cell division, for example: root, embryos, fruits etc. Coconut water is the liquid endosperm, the actively dividing tissue which serves as nutrition source for developing coconut embryo. Coconut water is used as growth promoter of developing embryos in tissue culture studies. It stimulates the growth of cultures of embryo due to presence of cytokinins. This makes option D correct. Abscisic acid (ABA) is a growth retardation hormone which inhibits seed germination and seedling growth. This makes option C incorrect as endosperm does not have growth retardation hormone. Option A is incorrect as auxin is the hormone of cell division and cell expansion, i.e., overall growth, while endosperm carries the hormone for cell division to increase the cell number only. Option B is incorrect as gibberellins are the hormone of stem elongation in genetic dwarf plants only.

Thus, the correct answer is option D.

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

Cell division is initiated by

  1. Cytokinin

  2. Auxin

  3. Gibberellin

  4. ABA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The cytokinin hormones promote cell division and tissue growth, and depend upon the presence of auxins to determine the extent of their activity. When the ratio of cytokinins to auxins is relatively high, stem and leaf growth is stimulated. 

So the correct option is 'Cytokinin'.

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

Natural hormone isolated from coconut milk and corn kernels is

  1. Florigen
  2. ${GA} _{3}$

  3. Auxins

  4. Zeatin
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Zeatin is a type of cytokinin, a plant hormone. It stimulates cell division. It is present in coconut milk. It was first isolated from Zea maize (corn kernels). It stimulates growth in plants. 

Thus, the correct answer is option D.

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

Which one is growth regulator produced by plants?

  1. NAA

  2. Zeatin

  3. 2, 4-D

  4. BAP
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Naphthaleneacetic acid (NAA) is a type of synthetic auxin, plant hormone. It is a growth regulator. It acts as rooting agent. Zeatin a type of naturally occurring cytokinin, the plant hormone. It was first discovered in Zea maize. A 2, 4-D is a type of synthetic auxin, plant hormone. It acts as weedicide. BAP (Benzylaminopurine) is a type of synthetic cytokinin, a plant hormone. It is involved in various physiological processes of plants like cell division.

Thus, the correct answer is option B.

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

Cytokinins which have specific effect in cytokinesis are modified forms of

  1. Cytosine

  2. Adenine

  3. Guanine

  4. Thiamine
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Cytokinin is a plant hormone. It has the specific effect in cytokinesis in plants. It is modified form of adenine. Kinetin, zeatin, and 6-benzylaminopurine are adenine type cytokinins. It is adenine molecule that is modified by the addition of 5-carbon sidechains off the 6 position.

Thus, the correct answer is option B.

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

Plant hormones used for inducing morphogenesis in plant tissue culture is

  1. Gibberellins

  2. Ethylene

  3. Cytokinins

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

Morphogenesis is the process of development of shape of an organism. Cytokinins which is present at the site where rapid cell division occurs like root apices, developing shoot buds it helps in plant growth and attaining its shape. So it will help the plant to maintain its shape in tissue culture.

So the correct option is 'Cytokinins'.