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 of the following plant hormones is/are activated in leaves by the process of vernalisation?

  1. Morphactin

  2. Florigen

  3. Jasmonates

  4. Karrikins

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

Vernalisation is the acquisition of a plant's ability to flower or germinate in the spring by exposure to the prolonged cold of winter. Vernalisation activates a plant hormone called florigen present in the leaves, which induces flowering at the end of the chilling treatment. Florigen or flowering hormone is the hypothesised hormone-like molecules responsible for controlling and/or triggering flowering in plants. Florigen is produced in the leaves and acts in the shoot apical meristem of buds and growing tips.

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. i, ii and iii only

  2. i, iv and v only

  3. ii and iv only

  4. iii and v only

  5. iii, iv and v only
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 senescence senescence and death plant growth plant growth and development biology

Senescense in plants leads into .......... of cells.

  1. Increase in size

  2. Increase in number

  3. Death

  4. Differentiation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Senescence also known as aging refers to the decrease in the functional capacity of an organism. This results in a cellular breakdown followed by metabolic failure. The death of cells followed by the death of plant is seen in senescence. Thus the correct answer is option C.

Multiple choice senescence senescence and death plant growth plant growth and development biology

Senescence of detached leaves can be delayed by the use of.

  1. Auxin

  2. Giberellin

  3. Cytokinin

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

Cytokinins are plant hormones that promote cell division and are famously known for delaying leaf senescence and chlorophyll degradation in detached leaves. Auxins and gibberellins have different primary growth roles, while ethylene typically accelerates ripening and senescence.

Multiple choice senescence senescence and death plant growth plant growth and development biology

The induction of cell elongation by IAA is explained on the basis of ______________.

  1. The acid growth hypothesis

  2. Auxin-ethylene balance hypothesis

  3. Sodium-potassium pump hypothesis

  4. Osmotic pressure hypothesis
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The acid growth hypothesis explains that auxin (IAA) stimulates proton pumps to acidify the cell wall, activating enzymes that loosen the wall and allow for cell elongation.

Multiple choice senescence senescence and death plant growth plant growth and development biology

Senescence is?

  1. A process of shedding leaves

  2. An irreversible catabolic phase of the aging process

  3. A process of shedding flowers

  4. A reversible metabolic phase in the growth of the plant
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Senescence is defined as the programmed, irreversible catabolic phase of the aging process that leads to structural degradation and eventual death of a cell, organ, or organism. It is an internal, regulated phase rather than a reversible metabolic state.

Multiple choice senescence senescence and death plant growth plant growth and development biology

Senescence in plants leads into .......... of cells.

  1. Increase in size

  2. Increase in number

  3. Death

  4. Differentiation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Senescence in plants is a process of aging. During process of senescence, cells undergo differentiation. It ultimately leads into the death of cells. 

Thus, the correct answer is option C.

Multiple choice biology living organisms and their surroundings living organism living vs nonliving living vs non living

Which one regulates plant growth?

  1. Commensalism

  2. Climate

  3. Hormones

  4. Both B and C
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

There are various plant hormones which regulate plant growth. Hormones like auxin, gibberellin, cytokinin promotes growth whereas hormones like ethylene and abscisic acid inhibits growth. Plant growth is also regulated by the climate or atmosphere. Various climatic factors like rainfall, light, temperature, humidity, etc regulates plant growth and development.

Thus, the correct answer is option D.