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

Which among the following is a phytohormone?

  1. Indoline

  2. Indole-3-acetic acid

  3. Inositol

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

Indole-3-acetic acid is a heterocyclic compound that is a phytohormone called auxin. This colourless solid is native plant compound, potent and the most important auxin. The molecule is derived from indole and containing a carboxymethyl group (acetic acid).

Multiple choice

The term stress hormone is used to refer

  1. ethylene

  2. ABA

  3. gibberellins

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

ABA is a stress hormone. Abscisic acid appears to maintain winter dormancy in buds. It prevents seeds from germinating while still attached to the parent plant, and it inhibits stem elongation. Through its effects on stomatal opening, it also regulates gas and water exchange between leaves and the atmosphere.

Multiple choice

The famous Avena curvature test conducted by F.W. Went proves that

  1. Plant growth regulators are auxins.

  2. Shoot apex is the site for the synthesis of growth regulating substance. .

  3. ABA is a growth inhibitor.

  4. Auxins exercise apical bud dominance.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The famous Avena curvature test conducted by F.W. Went proves that shoot apex is the site for the synthesis of growth regulating substance.

Multiple choice

Which among the following mechanisms of action of a herbicide affects the cell membrane production in the meristems of the grass plant leading to its death?

  1. ACCase inhibitors

  2. EPSPS inhibitors

  3. Synthetic auxins

  4. Photosystem I inhibitors

  5. Photosystem II inhibitors
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

ACCase inhibitors compounds kill grasses. Acetyl coenzyme A carboxylase (ACCase) is part of the first step of lipid synthesis. Thus, ACCase inhibitors affect cell membrane production in the meristems of the grass plant. The ACCases of grasses are sensitive to these herbicides, whereas the ACCases of dicot plants are not.

Multiple choice

Mobilization of stored food in germinating seeds is triggered by the hormone

  1. auxin

  2. gibberellin

  3. ethylene

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

The mobilization of reserve material from endosperm to the developing embryo is brought about by gibberellin through synthesizing hydrolysing enzyme (e.g., amylase and protease) which cause the breakdown of starch and proteins respectively. Sugar and amino acids so formed are transferred to the developing embryo.

Multiple choice

Which among the following statements regarding the growth and development of angiosperms is incorrect?

  1. Angiosperms grow continuously throughout their lives.

  2. Primary growth takes place in young, herbaceous organs of the plants.

  3. Monocots and herbaceous dicots typically exhibit only secondary growth.

  4. Cell and organ differentiation are usually regulated by the interaction of several hormones.

  5. All physiological activities of plants are directly related to temperature.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Monocots and herbaceous dicots typically exhibit only primary growth.The important factors affecting plant growth and development include heredity, hormones, nutrition, and environment.

Multiple choice

Which of the following types of oscillating gene present in plants regulates the expression of CAB?

  1. Toc1 gene

  2. The LHY gene

  3. The CCA1 gene

  4. Kai genes

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

Toc1 gene, also known as Timing of CAB Expression 1 gene, is an oscillating gene found in the plants that is known to control the expression of CAB. It has been shown to affect the period of circadian rhythms through its repression of transcription factors. This was found through mutations of toc1 in plants that had shortened period of CAB expression.

Multiple choice

The hormone present in the liquid endosperm of coconut is

  1. cytokinin

  2. gibberellin

  3. ethylene

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

Coconut water (liquid endosperm) is rich in cytokinins, which promote cell division. It's widely used in tissue culture media. Gibberellins promote stem elongation, ethylene controls fruit ripening, and auxin regulates cell elongation and apical dominance.

Multiple choice

The phytohormone, which influences apical dominance growth is

  1. IAA

  2. ABA

  3. GA3

  4. C2H4
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

IAA (Indole-3-Acetic Acid), the natural auxin, is primarily responsible for apical dominance - where the main shoot tip suppresses lateral bud growth. ABA (abscisic acid) is a stress hormone, GA3 promotes elongation and flowering, and C2H4 is ethylene (ripening hormone).