Biology

Plant Growth and Hormones

727 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

Which is the role not played by ethylene?

  1. Inhibition of elongation of stem.

  2. It increases the number of female flowers and reduces the number of male flowers.

  3. It causes ripening of fruits.

  4. It causes abscission of leaves.

  5. It increases maleness in some plants.
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This function is promoted by gibberellin.

Multiple choice

Which is not the specific function of auxin?

  1. Helps in apical dominance.

  2. Induces parthenocarpy

  3. Control of weeds

  4. Prevention of lodging

  5. Fruit ripening
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

It is the exclusive feature of ethylene and not auxins.

Multiple choice

Which hormone is antagonistic to activity of auxins?

  1. Cytokinin

  2. Gibberellin

  3. Calcitonin

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

Abscisic acid is a growth inhibitor and acts as an opponent to the activity of auxins. Auxins have a cardinal role in the coordination of many growth and behavioural processes in the plant's life cycle and are essential for the development of plant body. 

Multiple choice

Find the mismatched pair:

  1. Cytokinin : promotes cell division

  2. Auxin : cell enlargement

  3. Ethylene : phototropism in shoot

  4. Abscisic acid : wilting of leaves
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ethylene is a fruit ripening hormone.

Multiple choice

Which plant hormone is synthesized in shoot tips?

  1. Auxin

  2. Cytokinin

  3. Abscisic acid

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

Auxin is synthesised in shoot tips. Indole-3-acetic acid (IAA) is the most abundant and the basic auxin natively occurring and functioning in plants. It generates the majority of auxin effects in intact plants, and is the most potent native auxin.

Multiple choice

Which of the following statements are true regarding gibberellins? P. Gibberellin was named after the fungus gibberella africana. Q. Gibberellins are chemically terpenoid derivatives. R. Gibberellic acid is a dihydroxylated gibberellin. S. GA1 was the first gibberellin to be structurally characterized. Select the correct answer using codes given below:

  1. P and Q

  2. P and R

  3. P and S

  4. Q and R

  5. R and S
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Gibberellin was named after the fungus gibberella fujikuroi. Gibberellin was first isolated in 1935 by Teijiro Yabuta and Sumuki, from fungal strains (gibberella fujikuroi). Gibberellic acid (GA3) was the first gibberellin to be structurally characterized.

Multiple choice

Which of the following is a stress hormone?

  1. Benzyl aminopurine

  2. Dichloro acetic acid

  3. Abscisic acid

  4. Auxin

  5. Oxaloacetic acid
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

It promotes leaf detachment which induces dormancy and inhibits germination.

Multiple choice

Which of the following are examples of natural plant growth regulators?

i. IAA ii. GA3 iii. Zeatin iv. 2,4-D v. IBA

  1. Only i, ii and iii

  2. Only i, iv and v

  3. Only ii and iv

  4. Only iii and v

  5. Only iii, iv and v
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

All are natural plant growth regulators. Indole-3-acetic acid (IAA) is the most common, naturally-occurring, natural plant growth regulator hormone of the auxin class. Gibberellic Acid (GA3) is an important natural plant growth regulator that is used commercially to increase plant growth and crop yields. Zeatin is a member of the plant growth regulator hormone family known as cytokinins.

Multiple choice

Vernalisation can be replaced by

  1. cytokinins

  2. ethylene

  3. gibberlins

  4. abscisic acid

  5. NA
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Vernalisation can be replaced by Gibberlins. They are acidic in nature and its application increases the sugar yield by promoting internodal growth. Hence, it is the correct answer.