Tag: auxins and gibberellins

Quizzes (0) Questions (42)

Questions Related to auxins and gibberellins

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

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

  1. Cell division

  2. Phototropism

  3. Apical dominance

  4. Geotropism
Reveal answer Fill a bubble to check yourself
C Correct answer
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'.

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

Apical dominance is the function of Auxin.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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. 

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

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
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. 

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

The phenomenon of apical dominance is strenthened by

  1. Removal of the tiip

  2. Removal of leaves

  3. Auxin production

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
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.

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

Apical dominance means

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

Apical dominance is the phenomenon where the apical bud (the main growing tip) inhibits the growth of lateral (axillary) buds through the production of auxins.

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

Name the plant hormone associated with apical dominance.

  1. Auxin

  2. Ethylene

  3. Cytokinin

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • Apical dominance is a phenomenon wherby, the inhibition of the growth of lateral buds occurs due to the terminal bud of a shoot.
  • It is caused by the production of IAA (auxin) in abundance by the apical bud.
  • This auxin is transported basipetally from the apical bud.
  • The auxin causes the lateral buds to remain dormant. 
Multiple choice apical dominance auxins and gibberellins growth and development plant growth and development biology

Avena coleoptile test to find out the amount of growth promoting hormones was discovered by

  1. F W. Went

  2. LJ.Odum

  3. K.V Thimann

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

F. W. Went in 1928 used tip of Avena coleoptile. He removed the tip of Avena coleoptile and and placed in on the agar agar block for the definite measured amount of time. Then this agar agar block was placed asymmetrically on the stump, this showed a positive curvature. 

When this agar agar block was placed centrally on the stump then the growth of the coleoptile was found to be renewed. He named this growth promoting substance or hormone as auxin. 
He also noticed that curvature in Avena coleoptile is proportional, to the amount of auxin in agar agar block. Hence, option A is correct. 

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

The discovery, that during light induced bending of stem the apex produces a diffusible chemical, was made by

  1. Charles Darwin and Francis Darwin

  2. Boysen-Jensen and Paal

  3. Went

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

A tropism is a growth movement by plant part in the direction of the stimulus. According to Boysen-Jensen, the stimulus for phototropism, growth in response to light, is a diffusible chemical that passes from the tip of the coleoptile. He cut the tip of the coleoptile and the severed tip was reattached through a gelatin disc. The recapitated coleoptile showed bending of stem towards light. Paal continued with Boyse-Jensen work. He said that the tip of coleoptile produces some chemical which travels down and stimulates growth. The light causes the accumulation of that chemical on the shaded side of the coleoptile. 

Thus, the correct answer is option B. 

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

Decapitation i.e. removal of shoot tips in a plant usually results in

  1. inactivation of lateral buds

  2. growth of lateral buds

  3. cessation of plant growth

  4. yellowing of leaves.
Reveal answer Fill a bubble to check yourself
B Correct answer
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 'growth of lateral buds'.
Multiple choice apical dominance auxins and gibberellins growth and development plant growth and development biology

Growth hormone responsible for apical dominance is

  1. Auxin

  2. Cytokinin

  3. Gibberellin

  4. Ethylene
Reveal answer Fill a bubble to check yourself
A Correct answer
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 and cytokinin hormone is responsible for breaking the apical dominance. 

Thus, the correct answer is option A.