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 biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Match the columns and find the correct combination:

      I             II
a Auxin 1. Herring sperm DNA
b Cytokinin 2. Inhibitor of growth
c Gibberellin 3. Apical dominance
d Ethylene 4. Epinasty
e Abscisic acid 5. Induces amylase synthesis

  1. a- 3, b- 1, c- 5, d- 4, e- 2

  2. a- 4, b- 5, c- 1, d- 3, e- 2

  3. a- 2, b- 1, c- 5, d- 3, e- 4

  4. a- 3, b- 1, c- 5, d- 2, e- 4

  5. a- 4, b- 1, c- 5, d- 3, e- 2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Kinetin, a type of cytokinin was isolated from autoclaved herring sperm DNA. It has cell division-promoting activity. Auxin is a plant hormone. It promotes stem elongation and thus regulates apical dominance. Gibberellic acid is a plant hormone which breaks the dormancy. Before germination, it stimulates the synthesis of amylase enzyme. Amylase hydrolyzes starch into glucose which is used to provide nourishment to the seed embryo. Ethylene is a plant hormone that causes the downward bending of the plant part. This is called as epinasty. Abscisic acid is a plant hormone that acts as the inhibitor of growth.
Thus, the correct answer is option A.
Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Pick up correct statements.
(A) Cytokinins delay senescence
(B) Auxins regulate apical dominance
(C) Ethylene enhances seed germination
(D) Gibberellins cause falling of immature leaves

  1. $a, c$
  2. $a, d$
  3. $a, b$
  4. $b, c$
  5. $b, d$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cytokinin is a plant hormone that promotes cell division. It delays senescence. Auxin promotes stem elongation and thus regulate apical dominance. Ethylene is also called as ripening hormone as it helps in the ripening of fruits. Gibberellic acid prevents falling of immature leaves. 

Thus, the correct answer is option C.

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Match the columns and choose the correct combination.

Growth Regulator    Action
$(a)$ Abscisic acid $(1)$ Delays leaf abscission
$(b)$ Ethylene $(2)$ Inhibits seed germination
$(c)$ Cytokinin $(3)$ Herbicide
$(d)$ Auxin $(4)$ Hastens fruit ripening
  1. $a - 2, b - 4, c - 1, d - 3$
  2. $a - 1, b - 2, c - 3, d - 4$
  3. $a - 2, b - 3, c - 4, d - 1$
  4. $a - 2, b - 1, c - 3, d - 4$
  5. $a - 3, b - 4, c - 1, d - 2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Abscisic acid is a plant hormone. It is also called as stress hormone as its concentration increases during stress condition. During unfavorable environmental condition, it inhibits seed germination and induces seed dormancy. Ethylene is a plant hormone. It is also called as ripening hormone as it hastens fruit ripening in plants. Cytokinin is a plant hormone that induces cell division. It delays the abscission of leaves. A 2, 4-D is a synthetic auxin, a plant hormone. It acts as herbicide as it kills weeds.

Thus, the correct answer is 'a−2,b−4,c−1,d−3'.

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Which of the following pairs are correctly matched?
a. Auxin- Dwarf rice
b. Gibberellin- Elongation
c. Cytokinin- Coconut milk
d. Abscisic acid- Early leaf fall.
Select the correct answer using the codes given.

  1. $2, 3$ and $4$
  2. $1, 2$ and $3$
  3. $1, 2$ and $4$
  4. $1, 3$ and $4$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Gibberellin causes internode elongation (2), Cytokinin is found in coconut milk (3), and Abscisic acid promotes leaf senescence/fall (4). Auxin is not primarily associated with dwarf rice (that is Gibberellin).

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Which of the following chemicals are added in the synthetic media for culturing plant tissues?
a. Auxins
b. Cycloheximide
c. Cytokinins
d. Casein hydrolysate
Select the correct answer using the codes given.

  1. $1, 2$ and $3$
  2. $2, 3$ and $4$
  3. $1, 3$ and $4$
  4. $1, 2$ and $4$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Match List I(Plant hormone) with List II(Typica physiological effect) and select the correct answer using the code given the lists.

List-I List-II
a. Auxin $1$. Apical dominance
b. Gibberellins $2$. Cell division
c. Cytokine $3$. Fruit ripening
d. Ethylene $4$. Internodes elongation
  1. A-$1$, B-$4$, C-$2$, D-$3$
  2. A-$1$, B-$4$, C-$3$, D-$2$
  3. A-$4$, B-$1$, C-$2$, D-$3$
  4. A-$4$, B-$1$, C-$3$, D-$2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Auxin (1-Apical dominance), Gibberellins (4-Internode elongation), Cytokinin (2-Cell division), Ethylene (3-Fruit ripening).

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Read the given statements and identify the  plant hormones X,Y and Z
i) Hormone Y includes flowering in mango
ii) Hormone X promotes root growth and root hair formation
iii) Hormone Z inhibits the speed germination,increases the tolerance of the plant to various stresses ,play important role in speed development, maturation and dormancy.

  1. Y : ABA X : ausin Z : GA

  2. Z : GA X : Auxin Z :C2H4

  3. Y : Auxin X : C2H4 Z : GA

  4. Y : C2H4 X : C2H4 Z : ABA
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

The substance that triggers the fall of mature leaves and fruits from plants is

  1. Auxin

  2. Gibberellin

  3. Abscisic acid

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

Phytohormones are important plant growth regulators. The phytohormones, like auxins and gibberellins (GA), have positive growth-promoting effects whereas abscisic acid (ABA) and ethylene have growth inhibiting effects. Abscisic acid (ABA) was discovered for its role in regulating abscission and dormancy. It triggers fall of mature leaves and fruits from plants. Hence, it is called abscisic acid because of the formation of abscission layer which is responsible for fall of mature leaves and fruits from plants.  But like other PGRs, abscisic acid also has other wide-ranging effects on plant growth and development. It acts as a general plant growth inhibitor and an inhibitor of plant metabolism. ABA inhibits seed germination. ABA stimulates the closure of stomata in the epidermis and increases the tolerance of plants to various kinds of stresses. Therefore, it is also called the stress hormone. ABA plays an important role in seed development, maturation and dormancy. By inducing dormancy, ABA helps seeds to withstand desiccation and other factors unfavorable for growth. In most situations, ABA acts as an antagonist to GAs.

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Choose the correct answer from the alternatives given.
Which of the following statements about plant hormones is not true?

  1. Each naturally occurring hormone has a specific chemical structure

  2. Hormones are among the principal internal regulators of plant growth

  3. Responses to plant hormones may be observed in nearly any part of a plant

  4. All known growth regulators of plant activities are chemicals produced naturally in plants
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Cytokinins have specific effects on cytokinesis and were discovered as kinetin (a modified form of adenine, a purine) from the autoclaved herring sperm DNA. Kinetin does not occur naturally in plants.

So, the correct option is 'All known growth regulators of plant activities are chemicals produced naturally in plants'.

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Choose the correct answer from the alternatives given.
Plant hormones

  1. interact with one another

  2. are influenced by environmental cues

  3. are active in plant embryos within seeds

  4. all of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Plant hormones can work in combination and are dependent on the environmental cues or signals to act. They are also active in plant embryos within the seed such as Gibberellic acid.

So, the correct option is 'all of the above'.

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Choose the correct answer from the alternatives given.
The plant hormone that causes cell elongation is:

  1. citric acid

  2. indole 3-acetic acid

  3. ethylene

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

Plant cells elongate irreversibly only when load-bearing bonds in the walls are cleaved. Auxin causes the elongation of stem and coleoptile cells by promoting wall loosening via cleavage of these bonds. This process may be coupled with the intercalation of new cell wall polymers.

So, the correct option is 'indole 3-acetic acid'.

Multiple choice biology life processes: control and coordination control and coordination in plants growth in plants chemical coordination in plants animal senses sense organs in animals sense organs in humans

Find the odd man out:

  1. Auxin

  2. Abscisic acid

  3. Thyroxine

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

  • Auxin is a plant hormone that is produced in the tip of the stem that works in elongation.
  •  Auxin helps the plant to move to the darker side, the cell grows larger than corresponding cells present on the lighter side of the plant.
So, the correct option is 'Auxin'.