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 general knowledge

Ripening of harmone is :

  1. Gibberellin

  2. Morphaetin

  3. Ethylene

  4. I.B.A
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ethylene is the plant hormone responsible for initiating and regulating fruit ripening. It triggers the conversion of starch to sugar, color changes, and softening of fruits. Gibberellins promote stem elongation, while IBA (Indole-3-butyric acid) is a synthetic rooting hormone.

Multiple choice

Which of the following is not an application of gibberellin hormones of plants?

  1. Parthenocarpy

  2. Breaking of dormancy

  3. Increase in fruit size

  4. Delay in senescence

  5. In bolting
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Cytokinins delay the senescence of plant organs by controlling protein synthesis and mobilisation of resources. This phenomenon is called the Richmond Lang effect. They help produce chloroplast in leaves. These are also called anti-ageing hormones.

Multiple choice

The plant hormone having polar movement in downward direction is ______________.

  1. auxin

  2. abscisic acid

  3. ethylene

  4. gibberellic acid

  5. cytokinins
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

An auxin is manufactured primarily in the shoot tips (in leaf primordia and young leaves), in embryos, and in parts of developing flowers and seeds. Its transport from cell to cell, through the parenchyma surrounding the vascular tissues, requires the expenditure of ATP energy. IAA moves in one direction only, that is the movement is polar and, in this case, downward.

Multiple choice

Which of the following statements regarding auxins is incorrect?

  1. They activate tropic responses.

  2. They activate a gene required for making a protein necessary for growth of the plant.

  3. They maintain apical dominance.

  4. They activate the differentiation of non-vascular tissue in the shoot apex.

  5. They activate cellular elongation.

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

They activate the differentiation of non-vascular tissue in the shoot apex. They activate the differentiation of vascular tissue in the shoot apex and in calluses. They also initiate division of the vascular cambium in the spring and promote growth of vascular tissue in healing of wounds.

Multiple choice

The main naturally occurring auxin is indole-3 acetic acid, IAA. It was first isolated from ____________.

  1. human urine

  2. human faeces

  3. corn germ oil

  4. human serum

  5. human plasma
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Natural auxin: It was first isolated from human urine by Kogl and Haagensmit. It was named as auxin-a. But later, Kogl obtained another auxin called auxin-b (auxentriolic acid) from corn germ oil and heteroauxin from human urine. Heteroauxin, also known as indole-3-acetic acid (IAA) is the best known natural auxin. Indole butyric acid is another natural auxin.

Multiple choice

Which of the following sets represents cytokinins?

  1. IAA, IBA, NAA

  2. Kinetin, Zeatin, BAP

  3. Kinetin, IAA, IBA

  4. Kinetin, Zeatin, IBA

  5. Zeatin, NAA, IBA
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Correct answer. Kinetin is a type of cytokinin, a class of plant hormone that promotes cell division. Zeatin is a plant hormone derived from the purine adenine. It is a member of the plant growth hormone family known as cytokinins. 6-Benzylaminopurine (BAP) is a first-generation synthetic cytokinin that elicits plant growth and development responses, setting blossoms and stimulating fruit richness by stimulating cell division.