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 biology chemical coordination in plants ethylene plant hormones plants and animal hormones

Which of the following is a gaseous hormone?

  1. Auxin

  2. Ethylene

  3. Cytokinin

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

Ethylene is a volatile compound and the only gaseous plant growth hormone which is mainly found in ripening fruits, flowers and leaves. Its unsaturated nature and small structure make it a volatile compound. It is responsible for fruit ripening and induction of leaf senescence. This makes option B correct. Auxins are growth hormones that stimulate growth by cell division and cell elongation. They are synthesized in shoot and root tip and are also used as weedicide that selectively acts against certain weeds. Auxins includes IAA, IBA and 2,4-D which are complex compounds and are not gaseous. Cytokinins stimulate cell division, even in non-meristematic cells, in presence of auxin. They are most abundant in the growing tissues which are active site of cell division, for example: root, embryos, fruits etc. They are substituted adenosine compounds and are not gaseous. Gibberellins are hormones of bolting (stem elongation) and reversal dwarfism by increasing the internodal length. They are tetra carbocyclic compounds with characteristic gibbane skeleton having four rings of carbon and hence are not gaseous hormones. Thus, the correct answer is option B.

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

The most efficient precursor of ethylene is 

  1. Adenine

  2. Thiocarbamate

  3. Zeation

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

Two pathways for biosynthesis of ethylene in higher plants have been postulated. One is associated with the breakdown of peroxidized linolenic acid and the other involves degradation of methionine. 
A chemical mechanism accounting for such enzymatic formation of ethylene has been described. On the basis of this information, scientist has proposed the following scheme for the biosynthesis of ethylene in plants:
methionine -> alpha-keto-gamma-methylthiobutyric acid -+ methional--> ethylene.
In order to test the proposed pathways, radioactive linolenic acid and the appropriate radioactive methionine analogs were fed to apple tissue. None of these suggested precursors of ethylene was converted to ethylene as effectively as was methionine.

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

Plant hormone controlling fruit ripening is

  1. IAA

  2. GA

  3. Ethylene

  4. Kinetin
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 plays the important role in controlling the fruit ripening. During fruits ripening, the respiration rate in fruits is increased by ethylene. Due to increased respiration, complex carbohydrates are broken down into simpler sugars and cell wall becomes soft.

Thus, the correct answer is option C.

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

Which hormone is not translocated?

  1. Auxin

  2. Gibberellins

  3. ABA

  4. Cytokinin

  5. Ethylene
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Cytokinin is synthesized in the root and is translocated from roots to shoots via xylem. Auxin is synthesized in the stem tip and is translocated via parenchyma cells to different sites. Gibberellin is translocated via phloem and xylem. Abscisic acid is translocated through vascular tissue and activated diffusion. Ethylene is diffused through intracellular spaces throughout the plant as it is gaseous in nature.

Thus, the correct answer is option E.

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

How many following statements are correct for ethylene ?


1) Ethylene breaks the seed and bud dormancy
2) Ethylene promotes rapid petiole elongation in deep water rise plant
3) Ethylene promotes root growth and root hair formation
4) Ethylene promotes female flowers in cucumbers

  1. 1

  2. 2

  3. 3

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

Ethylene induces seed germination. It breaks seed and bud dormancy. So 1 is the right answer.

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

Choose the correct answer from the alternatives given.
Which of the following plant hormone is a gas?

  1. Auxin

  2. Cytokinin

  3. Ethylene

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

Ethylene is a small hydrocarbon gas. Ethylene is responsible for the changes in texture, softening, colour, and other processes involved in ripening. 

So, the correct option is 'Ethylene'.

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

Artificial ripening of fruits is caused by the treatment of

  1. IAA

  2. NAA

  3. Ethylene

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

Artificial ripening of fruits is caused by the treatment of ethylene. This process is achieved by spraying a commercial product Ethephon, that releases ethylene gradually on aerobic degradation. It is generally used for the faster ripening of cotton, wheat, coffee, tobacco, rice etc

So, the correct answer is 'Ethylene'

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

Gibberellins promote the formation of  A  flowers on genetically  B  plants in Cannabis whereas ethylene promotes formation of  C  flowers on genetically  D  Cannabis plants.

  1. A-male, B-female, C-female, D-male

  2. A-male, B-male, C-female, D-female

  3. A-female, B-male, C-male, D-female

  4. A-female, B-female, C-male, D-male
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Gibberellins are growth hormones that stimulate cell elongation and cause plants to grow taller. Gibberellins also have a role in other plant processes, such as stem elongation, germination, flowering, and fruit ripening. Gibberellins promote the formation of male flowers on genetically female plants in Cannabis whereas ethylene promotes formation of female flowers on genetically male Cannabis plants.
 So, the correct answers are "A- Male, B- Female, C- Female, D- Male."

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

A farmer grows cucumber plants in his field. He wants to increase the number of female flowers in them. Which plant growth regulator can be applied to achieve this?

  1. ABA

  2. Ethylene

  3. GA

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

Ethylene has a feminising effect on sex expression. The genetically male plants of cucumber can be induced to produce female flower in the presence of ethylene. The number of female flowers and hence fruit is enhanced in these plants.

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

Ethylene promotes senescence and is found in high concentration in ripened fruits.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Often considered an 'aging' hormone due to its role in accelerating such developmental processes as ripening, senescence, and abscission, the plant hormone ethylene also regulates many aspects of growth and development throughout the life cycle of the plant.

So, the correct answer is 'True'.
Multiple choice biology chemical coordination in plants ethylene plant hormones plants and animal hormones

Artificial ripening of fruits 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 a small hydrocarbon gas as well as a phytohormone. Some fruit will produce ethylene as ripening begins. Apples and pears are examples of fruit that produce ethylene with ripening. Ethylene is responsible for the changes in texture, softening, color, and other processes involved in ripening. Ethylene gas is used commercially to ripen tomatoes, bananas, pears, and a few other fruits postharvest.