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 apical dominance auxins and gibberellins growth and development plant growth and development biology

The phenomenon of apical dominance is strenthened by

  1. Removal of the tiip

  2. Removal of leaves

  3. Auxin production

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Auxin is an important plant hormone with a wide variety of effects. Auxin produced by the apical meristems inhibits the sprouting of lateral buds, and this phenomenon is called apical dominance. Apical dominance refers to an event in which the main stem of the plant grows more dominantly than the other branches on the stems. Production of auxin strengthens the phenomenon of apical dominance. Auxin inhibits the growth of lateral bud, and thereby allow the central stem to grow more vigorously.

Multiple choice apical dominance auxins and gibberellins growth and development plant growth and development biology

Apical dominance means

  1. Suppression of growth of apical bud by axillary buds .

  2. Supression of growth of axillary buds by the presence of apical bud.

  3. Stimulation of growth of axillary buds by removal of apical bud.

  4. Inhibition of growth of axillary buds by removal of the apical bud.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Apical dominance is the phenomenon where the apical bud (the main growing tip) inhibits the growth of lateral (axillary) buds through the production of auxins.

Multiple choice apical dominance auxins and gibberellins growth and development plant growth and development biology

Name the plant hormone associated with apical dominance.

  1. Auxin

  2. Ethylene

  3. Cytokinin

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • Apical dominance is a phenomenon wherby, the inhibition of the growth of lateral buds occurs due to the terminal bud of a shoot.
  • It is caused by the production of IAA (auxin) in abundance by the apical bud.
  • This auxin is transported basipetally from the apical bud.
  • The auxin causes the lateral buds to remain dormant. 
Multiple choice apical dominance auxins and gibberellins growth and development plant growth and development biology

Avena coleoptile test to find out the amount of growth promoting hormones was discovered by

  1. F W. Went

  2. LJ.Odum

  3. K.V Thimann

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

F. W. Went in 1928 used tip of Avena coleoptile. He removed the tip of Avena coleoptile and and placed in on the agar agar block for the definite measured amount of time. Then this agar agar block was placed asymmetrically on the stump, this showed a positive curvature. 

When this agar agar block was placed centrally on the stump then the growth of the coleoptile was found to be renewed. He named this growth promoting substance or hormone as auxin. 
He also noticed that curvature in Avena coleoptile is proportional, to the amount of auxin in agar agar block. Hence, option A is correct. 

Multiple choice apical dominance auxins and gibberellins growth and development plant growth and development biology

Growth hormone responsible for apical dominance is

  1. Auxin

  2. Cytokinin

  3. Gibberellin

  4. Ethylene
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 produced in the tip of the shoot. Auxin hormone is responsible for apical dominance and cytokinin hormone is responsible for breaking the apical dominance. 

Thus, the correct answer is option A.

Multiple choice apical dominance auxins and gibberellins growth and development plant growth and development biology

Substances which originate at the tip of stem and control growth elsewhere are

  1. Enzymes

  2. Hormones

  3. Vitamins

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

A chemical substance produced in one part of body and regulates the activity of other parts is called as hormones. Plant hormones are produced in the stem, bud and root tips and control the plant growth, formation of flowers, stems, leaves, development, and ripening of fruit, etc. Auxins are specialized hormones which acts on the tip.

Thus, the correct answer is option B.

Multiple choice apical dominance auxins and gibberellins growth and development plant growth and development biology

Apical dominance means

  1. Suppression of growth of apical bud by axillary buds

  2. Suppression of growth of axillary buds by the presence of apical buds

  3. Stimulation of growth of axillary buds by removal of apical buds

  4. Inhibition of growth of axillary buds by removal of apical buds
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Auxins are generally produced by the growing apices of the stems and roots, from where they migrate to the regions of their action. In most higher plants, the growing apical bud inhibits the growth of the lateral (axillary) buds, a phenomenon called as apical dominance. 

Apical dominance is thought to be due to production of auxins in the stem tips. Removal of shoot tips (decapitation) usually results in the growth of lateral buds. It is widely applied in tea plantations, hedge-making.

Multiple choice biology fruit and seed morphology of the fruit fruit plants: structure and function

The ripening of fruits can be accelerated by 

  1. Reducing the supply of water to plant when fruits are maturing

  2. Increasing the supply of nitrogen to the atmosphere surrounding them

  3. Warming up the surroundings artificially

  4. Artificially adding ethylene gas to the atmosphere surrounding them
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Ethylene is unique in that it found only in gaseous form, and accelerates ripening of fruits, leaves abscission and promotes senescence.

Multiple choice evs flow of water irrigation irrigation and its types irrigation and types

Farmers in a particular region were concerned that pre-mature yellowing of leaves of a pulse crop might cause decrease in the yield. Which treatment could be most beneficial to obtain maximum seed yield ?

  1. Frequent irrigation of the crop

  2. Treatment of the plants with cytokinins alongwith a small dose of nitrogenous fertilizer

  3. Removal of all yellow leaves and spraying the remaining green leaves with 2,4,5- trichlorophenoxy acetic acid

  4. Application of iron and magnesium to promote synthesis of chlorophyll
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
If a pulse crop possesses premature yellowing of leaves and decrease in yield then application of magnesium and iron to promote the synthesis of chlorophyll may become most beneficial to overcome the problem and to obtain maximum seed yield.  Magnesium is an important part of the ring structure of the chlorophyll molecule and its deficiency causes chlorosis and premature I leaf abscission. In iron deficiency also, the leaves become chlorotic because iron is required for the synthesis of some of the chlorophyll-protein complexes in the chloroplast.

So, the correct answer is 'Application of iron and magnesium to promote the synthesis of chlorophyll'.
Multiple choice botany modes of reproduction why do plants reproduce? reproduction and variation the life cycle of plants

Which of the following plant hormones is incorrectly paired with its function?

  1. Auxinpromotes stem growth through cell elongation

  2. Cytokinin initiates senescence

  3. Gibberellinstimulates seed and bud germination

  4. Abscisic acidpromotes seed and bud dormancy
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Natural cytokinins are synthesized in regions where rapid cell division occurs, for example, root apices, developing shoot buds, young fruits etc. They promote nutrient mobilization which helps in the delay of leaf senescence.

So, the correct option is 'Cytokinin initiates senescence'


Multiple choice botany root - external morphology morphology of the root root system in plants root

When a plant is not reproducing, most of its cytokinins are produced in its:

  1. Leaves

  2. Lateral buds

  3. Roots

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

The substance was named Cytokinin and it is involved in cell division and in the making of new plant organs, like a root or a shoot. Cytokinins are produced in the root apical meristems (very tip of the roots) and travel upward hitching a ride with water and traveling up the stem through the xylem.

So, the correct option is 'roots'.

Multiple choice botany plant biology introduction to angiosperms phanerogams angiosperms

Which one induces agamospermy in Apple?

  1. Hormones

  2. Low temperature

  3. Cross pollination

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

Agamospermy (apomixis) in various plants, including apple, can be induced or promoted by the application of specific plant growth hormones.

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Which one of the following is produced during stress conditions which leads to closure of stomata?

  1. Auxin

  2. ABA

  3. Cytokinin

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

Abscisic acid is a phytohormone critical for plant growth and development and plays an important role in integrating various stress signals and controlling downstream stress responses. Plants have to adjust ABA levels constantly in response to changing physiological and environmental conditions. ABA causes the closure of stomata. It thus helps in reducing the rate of transpiration.

Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Which one of the following acids is a derivative of carotenoids?

  1. Gibberellic acid

  2. Abscisic acid

  3. Indole butyric acid

  4. Indole-3-acetic acid
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Abscisic acid is also called as abscism. It is a plant hormone which has carotenoid as precursor. ABA functions in many plant developmental processes, including bud dormancy. ABA is an isoprenoid plant hormone, which is synthesized in the plastidal 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway, unlike the structurally related sesquiterpenes, which are formed from the mevalonic acid-derived precursor farnesyl diphosphate, the C15 backbone of ABA is formed after cleavage of C40 carotenoids in MEP.