Tag: auxins and gibberellins

Questions Related to auxins and gibberellins

Removal of apical bud makes the plant grow

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

  1. Tall

  2. Bushy

  3. Slow

  4. Rapidly

Show answer
Correct Option: B
Explanation:

Apical dominance is a phenomenon in which central stem is dominant and lateral stems are suppressed. It is due to plant hormones produced in the tip of the shoot. Auxin hormone is responsible for apical dominance. When apical bud is removed, lateral buds grow and the plant grows bushy.

Thus, the correct answer is option B.

Apical dominance in plants means

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

  1. Growth of lateral buds

  2. Inhibition of growth of lateral buds

  3. Both A and B

  4. None of the above

Show answer
Correct Option: B
Explanation:

Apical dominance is a phenomenon in which central stem is dominant and growth of lateral buds is inhibited. It is due to plant hormones produced in the tip of the shoot. Auxin hormone is responsible for apical dominance and cytokinin hormone is responsible for breaking the apical dominance. 

Thus, the correct answer is option B.

How many shoot aplical meristematic zones are expected in a twig of a plant possessing 9 branches, 39 leaves ?

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

  1. 9

  2. 39

  3. 10

  4. 8

Show answer
Correct Option: C
Explanation:

 Shoot apical meristem is the region in the growing shoot containing meristematic cells. The shoot apical meristem contains multipotent stem cells and produces primordia that develop into all the above-ground organs of a plant.it is always present at the growing apices.

Plants having 9 branches and 39 leaves will have 10 growing apices i.e shoot apical meristematic zones (9 growing apex of the branches +1 growing apex of the main plant axis ).
So, the correct answer is '10'.

In a garden, the gardener cut the apical bud of Lawsonia (mehandi) because 

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

  1. The length should be limited in Lawsonia.

  2. Due to the cutting of apical bud, the effect of Auxins decreases and lateral bud grows and forms dense appearance that is why it can give a definite shape.

  3. Other apical bud grows quickly due to cut of apical bud.

  4. Due to the cutting of apical bud effect of Ethylene decreases and the plant grows rapidly.

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Correct Option: B

In tea plantations and hedge making, gardeners trim the plants regularly so that they remain bushy. Scientific explanation behind this is

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

  1. Removal of apical dominance

  2. Growth of lateral buds

  3. Suppression of lateral buds

  4. Both (a) and (b)

Show answer
Correct Option: D
Explanation:

Auxin is a hormone present in plants at the tip of the stem. Its function is to maintain apical dominance (where main stem of the plant is dominant over other side branches) and to inhibit growth of lateral buds. That's why gardeners trim the plants regularly so that the plant grows laterally and remains bushy after removal of auxin.

Thus, the correct answer is 'Both (a) and (b).'

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.