Tag: plant growth and development

Questions Related to plant growth and development

In the proms of apical dominance, lateral buds are unable to grow in the presence of apical bud. This is due to

apical dominance auxins and gibberellins growth and development plant growth and development biology

  1. Less amount of auxin in apical bud

  2. More amount of auxin in apical bud

  3. Less amount of cytokinins in lateral buds

  4. More amount of cytokinins in lateral buds.

Show answer
Correct Option: B
Explanation:
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.
So the correct answer is 'More amount of auxin in apical bud'.

To get a carpet like grass, lawns are mowed regularly, this is done to

apical dominance auxins and gibberellins growth and development plant growth and development biology

  1. Remove the shoot apical meristem

  2. Remove the axillary buds

  3. Accelerate the growth of terminal bud

  4. Both (b) and (c)

Show answer
Correct Option: A
Explanation:

The lawn is mowed regularly to remove apical meristem, and prevent vertical growth of the grass and enhance the growth of lateral buds whose growth is hindered due to apical dominance. This helps the grass get a spreading or carpet like appearance.

So, the correct answer is 'Remove the shoot apical meristem'

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

apical dominance auxins and gibberellins growth and development plant growth and development biology

  1. promoted, promoted

  2. inhibited, inhibited

  3. promoted, inhibited

  4. inhibited, promoted

Show answer
Correct Option: D
Explanation:
Shedding of mature leaves from the stem or ripe fruits 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 the distal side and less auxin on the proximal side. The abscission zone formation occurs rapidly when the auxin gradient becomes slight or neutral. Moreover, the plant hormone ethylene is found to promote the abscission. Thus, a high concentration ocean prevents the formation of abscission layer and the phenomenon is controlled by the concentrations of auxin and ethylene. Apical dominance is promoted by auxin.
So the correct answer is "inhibited, promoted".

The hormone responsible for apical dominance is

apical dominance auxins and gibberellins growth and development plant growth and development biology

  1. IAA

  2. GA

  3. ABA

  4. Florigen

Show answer
Correct Option: A
Explanation:

Indole Acetic Acid IAA is a naturally produced hormone at the shoot tip by the apical bud that results in vertical growth of the stem, however, this inhibits the growth of lateral buds by preventing basipetal transportation of auxin. Which is termed as apical dominance.

So, the correct answer is 'IAA'

Phytohormone A causes apical dominance while phytohormone B overcomes the same. Select the option that correctly identifies A and B.

apical dominance auxins and gibberellins growth and development plant growth and development biology

  1. A-Auxin, B-Cytokinin

  2. A-Cytokinin, A-Auxin

  3. A-Gibberellin, B-Cytokinin

  4. A-Auxin, B-Gibberellin

Show answer
Correct Option: A
Explanation:

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

Auxin and cytokinin are antagonistic in which of the following functions?

apical dominance auxins and gibberellins growth and development plant growth and development biology

  1. Cell division

  2. Phototropism

  3. Apical dominance

  4. Geotropism

Show answer
Correct Option: C
Explanation:

Auxins are produced in the apical buds and they inhibit the growth of lateral buds on the stem thus leading to apical dominance. Whereas cytokinins promote the growth of lateral buds over and above the apical buds thereby antagonising the action of auxins.
So, the correct answer is, 'Apical dominance'.

Apical dominance is the function of Auxin.

apical dominance auxins and gibberellins growth and development plant growth and development biology

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Apical dominance is the condition in which an apical bud grows taller as compared to the other lateral branches. This is cause because apical bud produces IAA (Indole Acetic Acid) an auxin hormone in abundance. The presence of high concentration of auxin in the apical bud causes the lateral buds to remain dormant. It has been found that if apical bud is removed, the auxin concentration decreases which allows the lateral branches to grow. 

Thus, the correct answer is option A. 

Apical dominance - Auxin; Reversal of dwarfism - Gibberellins 
apical dominance auxins and gibberellins growth and development plant growth and development biology

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

Auxins are present in high concentrations in the tip of apical bud and their presence inhibits the growth of lower buds and branches. Thus one shoot becomes the tallest stem and other remain lower. This type of growth shown by apical bud in herbaceous plants is known as apical dominance. 

The major function of gibberellins is stem elongation causing the plants to grow taller. Gibberellins are responsible for increase in the internodal length in some genetically dwarf varieties such as Pea, Maize. 
Thus, the correct answer is option A. 

The phenomenon of apical dominance is strenthened by

apical dominance auxins and gibberellins growth and development plant growth and development biology

  1. Removal of the tiip

  2. Removal of leaves

  3. Auxin production

  4. none of these

Show answer
Correct Option: C
Explanation:

Auxin is an important plant hormone with a wide variety of effects. Auxin produced by the apical meristems inhibits the sprouting of lateral buds, and this phenomenon is called apical dominance. Apical dominance refers to an event in which the main stem of the plant grows more dominantly than the other branches on the stems. Production of auxin strengthens the phenomenon of apical dominance. Auxin inhibits the growth of lateral bud, and thereby allow the central stem to grow more vigorously.

Apical dominance means

apical dominance auxins and gibberellins growth and development plant growth and development biology

  1. Suppression of growth of apical bud by axillary buds .

  2. Supression of growth of axillary buds by the presence of apical bud.

  3. Stimulation of growth of axillary buds by removal of apical bud.

  4. Inhibition of growth of axillary buds by removal of the apical bud.

Show answer
Correct Option: B