Plant Hormones (Plant Physiology)

Total Questions: 11

1. Which one of the following is not a plant hormone? [U.P.P.C.S. (Mains) 2011]

Correct Answer: (c) Insulin
Solution:Insulin is a hormone produced in the pancreas by islets of Langerhans, which regulates the amount of glucose in the blood. The lack of insulin causes diabetes. Cytokinin, ethylene and gibberellin are plant hormones.

2. Which one of the following is a plant hormone? [U.P. R.O/A.R.O. (Mains) 2021, U.P.P.C.S. (Pre) (Re. Exam) 2015, U.P.P.C.S. (Mains) 2016]

Correct Answer: (d) Cytokinin
Solution:Plants need sunlight, water, oxygen, minerals for their growth and development. These are external factors. Apart from these, there are some intrinsic factors that regulate the growth and development of plants. These are called plant hormones or "Phytohormones".
  • Plant hormones are chemical compounds present in very low concentration in plants. They are derivatives of indole (auxins), terpenes (Gibberellins), adenine (Cytokinins), carotenoids (Abscisic acid) and gases (Ethylene).
  • These hormones are produced in almost all parts of the plant and are transmitted to various parts of the plant.
  • They may act synergistically or individually. Roles of different hormones can be complementary or antagonistic.
  • Hormones play an important role in the processes like vernalisation, phototropism, seed germination, dormancy etc. along with extrinsic factors.
  • Synthetic plant hormones are exogenously applied for controlled crop production.

3. Which of the following is a plant hormone? [Chhattisgarh P.C.S. (Pre) 2014]

Correct Answer: (d) Cytokinin
Solution:Plants need sunlight, water, oxygen, minerals for their growth and development. These are external factors. Apart from these, there are some intrinsic factors that regulate the growth and development of plants. These are called plant hormones or "Phytohormones".
  • Plant hormones are chemical compounds present in very low concentration in plants. They are derivatives of indole (auxins), terpenes (Gibberellins), adenine (Cytokinins), carotenoids (Abscisic acid) and gases (Ethylene).
  • These hormones are produced in almost all parts of the plant and are transmitted to various parts of the plant.
  • They may act synergistically or individually. Roles of different hormones can be complementary or antagonistic.
  • Hormones play an important role in the processes like vernalisation, phototropism, seed germination, dormancy etc. along with extrinsic factors.
  • Synthetic plant hormones are exogenously applied for controlled crop production.

4. Which one of the following is a plant hormone? [U.P. Lower Sub. (Pre) 2015]

Correct Answer: (b) Cytokinin
Solution:Plants need sunlight, water, oxygen, minerals for their growth and development. These are external factors. Apart from these, there are some intrinsic factors that regulate the growth and development of plants. These are called plant hormones or "Phytohormones".
  • Plant hormones are chemical compounds present in very low concentration in plants. They are derivatives of indole (auxins), terpenes (Gibberellins), adenine (Cytokinins), carotenoids (Abscisic acid) and gases (Ethylene).
  • These hormones are produced in almost all parts of the plant and are transmitted to various parts of the plant.
  • They may act synergistically or individually. Roles of different hormones can be complementary or antagonistic.
  • Hormones play an important role in the processes like vernalisation, phototropism, seed germination, dormancy etc. along with extrinsic factors.
  • Synthetic plant hormones are exogenously applied for controlled crop production.

5. Match List-I with List-II and select the correct answer from the code given below the lists: [U.P. R.O/A.R.O. (Mains) 2016]

 

List-IList-II
(Plant hormone)(Function)
A. Auxin1. Cell elongation
B. Gibberellin2. Cell division
C. Cytokinin3. Growth inhibition
D. Abscisic acid4. Apical dominance

Code:

 

CodeABCD
(a)2341
(b)4123
(c)3421
(d)4132
Correct Answer: (b)
Solution:The correctly matched lists of plant hormones and their functions are as follows:
List-IList-II
(Plant hormone)(Function)
AuxinApical dominance
GibberellinCell elongation
CytokininCell division
Abscisic acidGrowth inhibition

6. The hormone related to drought tolerance is - [U.P. Lower Sub. (Pre) 2013]

Correct Answer: (a) Abscisic acid
Solution:The hormone abscisic acid was discovered in the early 1960s and plant biologists have known for decades that it plays a crucial role in keeping plants alive during the drought. Abscisic acid causes the temporary closure of stomata when there is a shortage of water. It is very useful for the plants growing in water deficient soil. It functions as antitranspirant and also known as the stress hormone.

7. Which hormone is found in the gaseous form? [Chhattisgarh P.C.S (Pre) 2013]

Correct Answer: (b) Ethylene
Solution:Unlike other plant hormones like auxins, gibberellins, and cytokinins, which are typically present in solid or liquid form, ethylene exists as a gas. Ethylene is produced by plants in response to various stimuli, including aging, ripening, and stress.

Functions:

  • Fruit Ripening: Ethylene is a major regulator of fruit ripening, leading to changes in color, texture, and flavor.
  • Senescence and Abscission: It promotes the aging and shedding of leaves, flowers, and other plant organs.
  • Other Processes: Ethylene also influences seed germination, root growth, and the response to stress.

8. The gas used in the artificial ripening of green fruit is - [U.P.P.C.S. (Pre) 1996]

Correct Answer: (a) Acetylene
Solution:Under prevention of food adulteration rule, 1955: (Clause 44AA) acetylene gas cannot be used in the ripening of fruits. Calcium carbide is used in some countries as a source of acetylene gas, which is an artificial ripening agent. However, acetylene is not nearly as effective as ethylene and is not a natural plant hormone like ethylene.

Also, calcium carbide may contain traces of arsenic and phosphorus, both highly toxic to humans and the use of this chemical for ripening is illegal in most countries. Ethylene has been found not harmful or toxic to humans in the concentrations found in ripening rooms.

9. The gas used for artificial ripening of green fruits is - [Jharkhand P.C.S. (Pre) 2010, U.P. Lower Sub (Pre) 2008, U.P.P.C.S. (Mains) 2007]

Correct Answer: (b) Acetylene
Solution:Under prevention of food adulteration rule, 1955: (Clause 44AA) acetylene gas cannot be used in the ripening of fruits. Calcium carbide is used in some countries as a source of acetylene gas, which is an artificial ripening agent. However, acetylene is not nearly as effective as ethylene and is not a natural plant hormone like ethylene.

Also, calcium carbide may contain traces of arsenic and phosphorus, both highly toxic to humans and the use of this chemical for ripening is illegal in most countries. Ethylene has been found not harmful or toxic to humans in the concentrations found in ripening rooms.

10. Which of the following phytohormone is mainly responsible for fruit ripening? [U.P.P.C.S. (Mains) 2009, U.P.P.C.S. (Pre) 2006]

Correct Answer: (c) Ethylene
Solution:Under prevention of food adulteration rule, 1955: (Clause 44AA) acetylene gas cannot be used in the ripening of fruits. Calcium carbide is used in some countries as a source of acetylene gas, which is an artificial ripening agent. However, acetylene is not nearly as effective as ethylene and is not a natural plant hormone like ethylene.

Also, calcium carbide may contain traces of arsenic and phosphorus, both highly toxic to humans and the use of this chemical for ripening is illegal in most countries. Ethylene has been found not harmful or toxic to humans in the concentrations found in ripening rooms.