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 plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

One hormone stimulates the closure of stomata and another one influences the swelling of the axis in dicot plants. They are 

  1. Gibberellins and ethylene

  2. Abscisic acid and cytokinins

  3. Gibberellins and cytokinins

  4. Auxins and cytokinins

  5. Abscisic acid and ethylene
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Abscisic acid is a plant hormone. It is also called as a stress hormone. During adverse environmental conditions, it's concentration increases. During water stress condition, it stimulates closure of stomata and hence decreases transpiration rate. Ethylene is also a plant hormone. It shows the triple response. It influences the horizontal growth of seedlings, swelling of the axis and apical hook formation in dicot plants.

Thus, the correct answer is option E. 

Multiple choice biology plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Find out correct options.

   I      II      III
a Foolish plant p Volatile hormone x Induces dormancy
b Induces senescence q Abscisic acid y Ripens fruit
r Gibberella z Usually sterile plant

  1. a- p- y, b- r- x

  2. a- r- z, b- q- z

  3. a- r- z, b- p- y

  4. a- q- x, b- r- y
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The foolish seedling disease affects the rice plant through the roots or crowns. It is caused by the fungus Gibberella fujikuroi. It is the source of gibberellin hormone. The plant is usually sterile. Abscisic acid is a plant hormone that induces senescence in plants. Under stress environmental condition, it induces seed dormancy.

Thus, the correct answer is option B.

Multiple choice biology plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

The primary and secondary growth of a shoot is inhibited 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 plant hormone. It is growth inhibitor hormone. Its primary role is inhibition of growth of root, shoot, leaf, etc. It inhibits primary and secondary growth of shoot. During stress condition, its concentration increases.

Thus, the correct answer is option D.

Multiple choice biology plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

State whether the following statements are true or false.
A cut woody stem exposed to a cytokinin solution will be induced to grow roots rapidly.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

cytokinins are the plant growth regulators that promote cell division, they function similar to auxin and helps in cell elongation and are majorly present in the roots and then passes through the xylem. They perform many functions like cell division, embryo and endosperm formation, and growth of root cells etc.

So, the correct statement is 'True'.

Multiple choice biology plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Kinetin, a modified form of adenine was discovered from

  1. Autoclaved herring sperm DNA

  2. Coconut milk

  3. Corn kernel

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

Kinetin is a modified form of adenine which is discovered by Miller and Skoog as a compound from autoclaved herring sperm DNA. Herring is a fish. From it's sperm, DNA is isolated which is sterilized using steam at high pressure which is called autoclaved herring sperm DNA. From this, kinetin was isolated which has ability to induce cell division.

Thus, the correct answer is 'Autoclaved herring sperm DNA.'

Multiple choice biology plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Horizontal growth of seedlings, swelling of axis and apical hook formation in dicot seedlings is brought about by

  1. Auxins

  2. Gibberellins

  3. Ethylene

  4. Kinetin

  5. Abscisic acid
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Ethylene is a gaseous plant hormone. It is also called as ripening hormone as it stimulates ripening of fruits. It also promotes the horizontal growth of seedlings, swelling of the axis and increase curvature by apical hook formation in dicot seedlings. It inhibits stem elongation. This is called as triple response shown by ethylene.
Thus, the correct answer is option C.
Multiple choice biology plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Which is not the effect of ethylene?

  1. Promotes senescence and abscission of plant organs

  2. Breaks seed and bud dormancy

  3. Brings about horizontal growth of seedlings

  4. Hastens fruit ripening

  5. Helps to overcome apical dominance
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Ethylene is a plant hormone. It is also called as ripening hormone as it hastens fruit ripening in plants. In certain plants, it breaks seed and bud dormancy and induces germination. It also causes flowers to fall from the plant and hence, promotes senescence and abscission of plant hormones. It also causes the triple response in etiolated seedlings. It inhibits stem elongation and brings about the horizontal growth of seedlings. 

Thus, the correct answer is option E.

Multiple choice biology plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Artificial ripening of fruit is carried out by

  1. Auxin

  2. Gibberellin

  3. Abscisic acid

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

Ethylene is sprayed on fruits to promote artificial ripening, which is very commonly seen in fruit shops.
Ethylene is applied on fruits in the form of a spray. It acts to the fruit cell wall made of pectin or cellulose and promotes ripening.

Multiple choice biology plant growth and development other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Gibberellic acid is known to carry out all these functions except?

  1. Increase in yield in grapes and apple

  2. Speed up malting process
  3. Activation of $\alpha$-amylase

  4. Nutrient immobilisation in aleurone layer
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Gibberellic acid promotes cell elongation, seed germination, enzyme activation such as alpha-amylase in the aleurone layer, and fruit growth. It does not cause nutrient immobilization; rather, it mobilizes stored reserves during germination. Thus, nutrient immobilization is the exception.

Multiple choice biology plant growth and development other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Cycocel is a .............

  1. Wound hormone

  2. Growth hormone

  3. Rhizocaline necessary for root formation

  4. Growth retardant
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 Cycocel is among the most reliable and widely used plant growth regulators on the market. Cycocel may be used on any crop in the green house or nursery including but not limited to, poinsettias, hibiscus, azzaleas and geraniums to reduce stem elongation, induce early flowering, and to produce compact plants with multiple buds per shoots.

Multiple choice biology plant growth and development other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Elongation of internodes is inhibited by ..............

  1. Gibberellins

  2. Morphactins

  3. Both (A) and (B)

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Morphactins have inhibitory effect on the stem elongation. Increases concentration produced dwarfing in the plants. Morphactins are a group of substances which act on morphogenesis and modulate the expression of plants. Chemically, they are the derivatives of fluorene compounds.

Multiple choice biology plant growth and development other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Hormone produced during leaf fall is

  1. Cytokinin

  2. Florigen

  3. ABA

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

Leaf abscission is a detachment or fall of older leaves. It occurs at the base of the petiole. During leaf fall, high synthesis of abscisic acid is observed along with decrease in the concentration of auxin. It loosens the cell wall and cells separate which ultimately leads to leaf abscission

Thus, the correct answer is option C.

Multiple choice biology plant growth and development other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Under water stress, plants increase the synthesis of ______________.

  1. Gibberellic acid

  2. Cytokinin

  3. Auxins

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

Abscisic acid is known as the stress hormone in plants because its synthesis increases significantly under water stress or drought conditions. It triggers stomatal closure to minimize water loss through transpiration. The other listed hormones have different primary roles in growth and development.