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 chemical coordination in plants cytokinins plant hormones plants and animal hormones

Cytokinin was first synthesized by ...................

  1. Skoog and Miller

  2. Letham

  3. Bensan and Calvin

  4. Thimman and Went
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Cytokinins are a class of plant growth substances that promote cell division or cytokinesis in plant roots and shoots. They are involved primarily in cell growth and differentiation, but also affect apical dominance, axillary bud growth and leaf senescence. Letham first synthesized it from corn milk.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

An excised leaf does not turn yellow if it is induced to root. This is attributed to synthesis in root of ...................
or
Leaf ageing is retarded by ........................

  1. Ethylene

  2. Cytokinins

  3. Gibberellins

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

According to Richmond lang effect, cytokinin hormone in plants will cause retardation of chlorophyll and several other proteins. Thus, it helps in reducing the senescence.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

The cut flowers and vegetables can be kept fresh a long period by this

plant hormone ...............

  1. Gibberellins

  2. Cytokinins

  3. Auxins

  4. Ethylene

  5. 2,4 - dichlorophenoxy acetic acid
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Cytokinin is the plant hormone which is found to have profound effects in delaying the ageing of plant and thus increases the shelf life of vegtables and fruits. It acts by retarding the destruction and degeneration of chlorophyll and proteins. This is called as 'Richmond Lang effect'.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

A plant hormone used for inducing morphogenesis in plant tissue culture

is ........................

  1. Abscisic acid

  2. Gibberellins

  3. Cytokinins

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

Morphogenesis is the process of organ formation. Cytokinin is a plant hormone which plays a major role in organ formation or morphogenesis with the presence of auxin. It helps in rapid multiplication of cells by repeated cytokinesis and karyokinesis.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Cytokinins are mostly produced in

  1. Shoot apex

  2. Root apex

  3. Young leaves

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

Cytokinin is a plant hormone. It promotes cell division. It also delays the destruction of chlorophyll and protein. It shows delay of senescence in leaves.  It is mostly produced in the root apex. When an excised leaf is induced to root, it does not turn yellow because root apex synthesizes cytokinin hormone.

Thus, the correct answer is option B.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Delay in senescence is caused by the spray of 

  1. IBA

  2. GA

  3. Cytokinin

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

Senescence means aging. Cytokinin is a plant hormone. It plays major role in cell proliferation and cell division. During senescence, cytokinin levels are low. It delays in senescence of leaves when sprayed externally by delaying the destruction of chlorophyll and proteins in leaves. 

Thus, the correct answer is option C.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Cytokinins are generally

  1. Acids

  2. Aminopurines

  3. Phenols

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

The first cytokinin discovered was an aminopurine derivative named kinetin. Except zeatin which is adenine derivative, all other present cytokinins are aminopurines. All the naturally occurring cytokinins are substituted purines, in which sixth carbon is substituted by amino group.

Thus, the correct answer is option B.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Flowering in some short day plants is promoted by

  1. Auxins

  2. Gibberellins

  3. Cytokinins/ABA

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

Gibberellin is a plant hormone which helps in growth of stem. The rapid growth and flowering with cell division and cell elongation is called as bolting. Bolting requires either long days or cold treatment. Bolting can be induced by higher level of gibberellin under normal conditions. Hence, it induces flowering in some short day plants.

Thus, the correct answer is option B.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Cytokinins have the ability to

  1. Induce morphogenesis

  2. Substitute cold treatment

  3. Convert dwarf plants to tall plants

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

Cytokinins are plant hormones that are involved in various physiological processes. They promotes cell division by stimulating mitosis. Due to increased rate of mitosis, they induce shoot and root morphogenesis. They also plays important role in formation of fruits and seeds.

Thus, the correct answer is option A.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Cut pr excised leaves remain green for long if induced to root or dipped in

  1. Gibberellins

  2. Cytokinins

  3. Auxins

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

Cytokinin is a plant hormone. It promotes cell division. It also delays the destruction of chlorophyll and protein. It shows delay of senescence in leaves and keeps leaves green for long time. So when cut or excised leaves are induced to root, it will remain green because root synthesizes cytokinin hormone.

Thus, the correct answer is option B.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

The regulator which retards ageing senescence of plant parts is

  1. Cytokinin

  2. Auxin

  3. Gibberellin

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

Cytokinins is a plant hormone. It retards ageing senescence of plant parts and thus keep them productive for longer duration. This is called as Richmond Lang effect. It delays destruction of chlorophyll. It has an effect on protein synthesis and mobilizing nutrients. 

Thus, the correct answer is option A.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Cytokinins are mostly

  1. Glucosides

  2. Aminopurines

  3. Acidic

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

The first cytokinin discovered was an aminopurine derivative named kinetin. Except zeatin which is adenine derivative, all other present cytokinins are aminopurines. All the naturally occurring cytokinins are substituted purines, in which sixth carbon is substituted by amino group.

Thus, the correct answer is 'Glucosides'.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Hormone discovered through tissue culture technique is

  1. Auxin

  2. Cytokinin

  3. Gibberellin

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

Hormone discovered through tissue culture technique is cytokinin. Cytokinin was discovered by Skoog and Miller. The first cytokinin discovered was kinetin. This was isolated as a DNA degradation product. 

Thus, the correct answer is option B.

Multiple choice biology chemical coordination in plants cytokinins plant hormones plants and animal hormones

Hormone that promotes growth of lateral buds/has negative effect on apical dominance is

  1. Cytokinin

  2. Gibberellin

  3. Auxin

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

Apical dominance is a phenomenon in which central stem is dominant and lateral stems are suppressed. It is due to plant hormones auxin produced in the tip of the shoot. It promotes apical dominance and does not allow lateral / axillar buds to grow. Another plant hormone, cytokinin is responsible for having negative effect on the apical dominance. It promotes the growth of lateral buds.  

So, the correct answer is 'Cytokinin'