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 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 botany living world of plants - plant physiology historical events in photosynthesis history of photosynthesis introduction to photosynthesis

Which phytohormone is responsible for the promotion of female flowers in cucumber?

  1. $ABA$
  2. $GA _3$
  3. $C _2H _4$
  4. $C _2H _2$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Ethylene is a simple Gaseous PGR(Plant growth regulator). The hormone finds its use in increasing the yield of cucumber plant by increasing the female flower formation. 

So, the correct answer is 'Ethylene(C$ _2$H$ _4$)'.

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

A substance which is used to stimulate the increase in size of the apple fruit is 

  1. Morphactin

  2. Promalin

  3. Ethylene

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

Promalin is a mixture of cytokinin-6-benzaldenine, GA$ _{4}$ and GA$ _{7}$. It is very active in stimulating increase in apple size particularly in red delicious apples.

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.

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

A substance that induces dormancy in seed is

  1. ABA

  2. GA

  3. Thiourea

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

A substance that induces dormancy in seed is ABA. Abscisic acid (ABA), also known as abscisin II and dormin, is an isoprenoid plant hormone. ABA functions in many plant developmental processes, including bud dormancy. It is responsible for seed dormancy by inhibiting cell growth inhibits seed germination.

Thus, the correct answer is option A.

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

The hormone produced during adverse environment condition is ...............

  1. Abscisic acid
  2. $N^{6}$ - Isopentanyl adenine (CK)

  3. Dichlorophenoxy acetic acid, (2, 4 - D)

  4. Gibberellic acid (GA)
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Abscisic acid (ABA) was discovered for its role in regulating abscission and dormancy. But like other PGRs, it 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 unfavourable for growth. In most situations, ABA acts as an antagonist to gibberellins.

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

Which of the following is a stress hormone?

  1. Benzyl aminopurine

  2. Dichlorophenoxy acetic acid

  3. Ethylene

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

Despite its name, abscisic acid does not induce abscission in most plants. Instead, abscisic acid is involved in a plants response to stress and in seed dormancy, a temporary state of arrested physiological activity. As an environmental stress hormone, abscisic acid particularly promotes changes in plant tissues that are water stressed.

Thus, the correct answer is option D.

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

Abscisic acid induces .......................

  1. Shoot elongation

  2. Cell elongation and cell wall formation

  3. Cell division

  4. Leaf fall and dormancy
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Abscisic acid (ABA) was discovered for its role in regulating (leaf and fruit) abscission and dormancy. But like other PGRs, it 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 unfavourable for growth. In most situations, ABA acts as an antagonist to gibberellins
So, the correct answer is 'Leaf fall and dormancy'
Multiple choice biology chemical coordination in plants abscisic acid fruit plants: structure and function

Hormone produced during leaf fall is

  1. IAA

  2. ABA

  3. Florigen

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

Abscisic acid (ABA) was discovered for its role in regulating abscission and dormancy. It is the hormone believed to be responsible for controlled abscission of mature leaves and fruits from plants. But like other PGRs, it 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 as the stress hormone.

Thus, the correct answer is option B.