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 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 is a gaseous hormone?

  1. Kinetin

  2. Zeatin

  3. Auxin

  4. Ethylene
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • Ethylene is a gaseous hormone, which stimulates transverse or isodiametric growth but retards the longitudinal one. 
  • It is a gas that forms through the break down of methionine, which is in all cells. 
  • It has very limited solubility in water and does not accumulate within the cell but diffuses out of the cell and escapes out of the plant.
  • Thus, the correct option is D.
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

Closure of stomata is caused by 

  1. Auxin

  2. Gibberellin

  3. Cytokinin

  4. Abscisic Acid
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • Abscisic acid is a carotenoid-derived plant hormone known to regulate critical functions in growth, development and responses to environmental stress.
  • It plays a key role in the regulation of stomatal closure by regulating ion channel activities and water exchanges across the plasma membrane of guard cells.
  • It increases the influx of calcium ions and efflux of potassium ions, which results in the closure of stomata.
  • So, the correct option is D.
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

Of the following which plant hormone inhibits growth?

  1. Cytokynins

  2. Gibberelins

  3. Auxins

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

Abscisic acid is the plant growth hormone which is responsible for inhibiting growth. The hormone causes inhibition in the growth of the roots and shoots. The hormone also causes abscission which is the falling of the leaves, fruits and flowers. The hormone suppresses all the processes in the plants during unfavourable conditions. 

Thus, the correct answer is option D. 

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

Auxin does not increase

  1. The plasticity of cell walls

  2. The rate of photosynthesis

  3. The uptake of water by cells

  4. Rate of respiration
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Auxin is a plant hormone that plays important role in plant growth. It stimulates stem elongation by increasing permeability of cells which in turn increases uptake of water by cells. It also enhances plasticity of cell walls which results in cell enlargement. It also increases the respiration rate.

Thus, the correct answer is option B.

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

Leaf fall can be prevented with the help of 

  1. Abscisic acid

  2. Auxins

  3. Florigen

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

Leaf abscission is a detachment or fall of older leaves.It occurs at the base of the petiole. When auxin is applied to the base of petiole of young leaf, the abscission is greatly suppressed. Also, it is observed that the intact leaf does not fall off because it synthesizes auxin.

Thus, the correct answer is option B.

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 is not an influence of auxins?

  1. Tropical movements

  2. Bolting

  3. Parthenocarpy

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

Auxin is a plant hormone which is involved in various physiological processes. It is present on the tip of the stem and helps in phototropic movement in response to light. It also maintains apical dominance where there is more growth on the stem tip and growth of lateral bud is inhibited. Auxin along with cytokinin and gibberellin helps in the process of parthenocarpy. It does not cause bolting. It does not influence flowering in the plant.

Thus, the correct answer is option B.

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
C Correct answer
Explanation

Synthetic media for plant tissue culture commonly includes auxins and cytokinins for growth regulation, along with complex organic supplements like casein hydrolysate. Cycloheximide is a protein synthesis inhibitor and would harm tissue cultures.

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.