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 plant growth and development other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Choose the correct answer from the alternatives given.
Elongation of a genetically dwarf plant is possible by the application of:

  1. TAA

  2. GA3

  3. zeatin

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

Gibberellins (like GA3) are well-known for their ability to stimulate stem elongation and can overcome genetic dwarfism in plants by promoting internode growth.

Multiple choice biology plant growth and development other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Choose the correct answer from the alternatives given.
Spraying plants with a combination of auxins and gibberellins:

  1. promotes formation of parthenocarpic fruit

  2. kills broad-leaved dicot plants

  3. prevents senescence

  4. promotes fruit ripening
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When sprayed on flowers, any of the plant hormones gibberellin, auxin and cytokinin could stimulate the development of parthenocarpic fruit.

So, the correct option is 'promotes the formation of parthenocarpic fruit'.

Multiple choice biology plant growth and development other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Choose the correct answer from the alternatives given.
Bolting of floral shoots is triggered by a high concentration of:

  1. auxin

  2. gibberellins

  3. cytokinins

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

Gibberellins also promote bolting (internode elongation just prior to flowering) in beet, cabbages and many plants with rosette habit.

So, the correct option is 'gibberellins'.

Multiple choice biology plant growth and development other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Which of the following is true?

  1. Cytokinins helps in ripening of fruit.

  2. Gibberellins helps in ripening of fruit.

  3. Calcium carbide helps in ripening of fruit.

  4. Calcium carbonate helps in ripening of fruit.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Calcium carbide is used for ripening fruit artificially in some countries. When calcium carbide comes in contact with moisture, it produces acetylene gas, which is quite similar in reaction to the natural ripening agent ethylene.

Thus, the correct answer is option C.

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

Delaying aging of leaves and opening of stomata are due to the action of _______

  1. Auxins

  2. Gibberellins

  3. Cytokinins

  4. Abscisic acid
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
A. Auxins are the plant hormones which promote cell enlargement and cell differentiation. It also promote fruit growth. It is responsible for phototropic and geotropic responses of plants.
B. Gibberellins are plant hormones which promote cell enlargement and cell differentiation in the presence of auxins. It help in breaking the dormancy in seeds and buds. It also promote fruit growth. It stimulates elongation of shoots of various plants.
C. Cytokinins are plant hormones which promote cell division in plants. It also helps in breaking the dormancy in seeds and buds. The delay the ageing of leaves. It promotes opening of stomata.
D. Abscisic acid (ABA) is a  plant hormone which functions mainly as a growth inhibitor. It promotes the dormancy in seeds and buds [ this is the opposite of breaking the dormancy. It also promotes closing of stomata. It promotes falling of leaves. 
So, the correct answer is 'Cytokinins'.

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

Cytokinins are known to

  1. Inhibit cytoplasmic movement.

  2. Help in retention of chlorophyll.

  3. Influence water movement.

  4. Promote abscission layer formation.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Cytokinins perform several other functions:
- Stimulates cell division.
- Stimulates morphogenesis in tissue culture.
- Stimulates the growth of lateral buds.
- Stimulates leaf expansion.
- Enhance stomatal opening

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

Cytokinin and ethylene have oppsite effect on:-

  1. Leaf senescence

  2. Elogation of stem

  3. Lateral swelling of stem

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

Cytokinins are the plant hormones that are responsible for cell division and elongation, their help in the delay of leaf senescence as they transport nutrients to these parts. Ethylene is a gaseous hormone and is responsible for transverse growth as swelling of the stem, It hastens the senescence of leaves due to the evolution of ethylene gas.

So, the correct option is 'Leaf senescence'.

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

Which one of the following is not true about kinetin?

  1. It promotes bud growth.

  2. It defers senescence.

  3. It helps in retention of chlorophyll.

  4. It inhibits the cell division.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Kinetin is a type of cytokinin, a class of plant hormone that promotes cell division. Kinetin was originally isolated by Miller and Skoog et al as a compound from autoclaved herring sperm DNA that had cell division-promoting activity.

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

A plant hormone which delays senescence and helps in cell division is .............

  1. Auxin

  2. Gybberellin

  3. Cytokinin

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

Cytokinins are the plant hormones which has manifold effects on plants. It includes delaying of senescence, active cell division and so on. Cytokinins increase cell division by stimulating proteins needed for mitosis. Mitosis is non-sexual cell division that occurs in all living things producing additional cells for body growth. The active principle responsible for inducing cell division was isolated first from the extracts of yeasts. Such a substance was called kientin, later the name was changed and called as cytokinin.

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

Richmond Lang effect is due to .........................

  1. Cytokinin

  2. Auxin

  3. ABA

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

Cytokinins are the phytohormones which can delay plant senescence by the stimulation of cell division. Cytokinins also prevent the destruction of chlorophyll and consequently the plant parts do not turn yellow. This is known as Richmond Lang effect after the workers who discovered it.

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

Cytokinin 

  1. Is a hormone whose main function is to induce the cell division.

  2. Is the process of cell division.

  3. Refers to cell division.

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

Cytokinins are phytohormones which have specific effects on cytokinesis and were discovered as kinetin (a modified form of adenine, a purine) from the autoclaved herring sperm DNA. Kinetin does 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. Since, the discovery of zeatin, several naturally occurring cytokinins and some synthetic compounds with cell division promoting activity, have been identified. Natural cytokinins are synthesised in regions where rapid cell division occurs, for example, root apices, developing shoot buds, young fruits etc.

Thus, the correct answer is option A.