WBBSE Solutions For Class 10 Life Science And Environment Chapter 1 Response And Chemical Co Ordination In Plants Hormones

Chapter 1 Response And Chemical Co-Ordination In Plants Hormones

Control of different function and coordination between them is regulated by hormone i.e. hormone helps in plant response.

The hormone regulates the apical growth of stem and root, lateral growth, flowering, bud formation, and germination of seed in plants.

Hormones thus control different types of growth and germination in plants. The main three hormones in plants are auxin, gibberellin, and cytokinin. Auxin is an organic acid with an indole ring and nitrogen.

It controls the apical dominance through increasing apical bud formation, cell division, root formation, and its growth and also controls the tropic movement.

Gibberellin is a terpenoid organic acid without nitrogen, It breaks the dormancy of bud and seed, increase the growth of internode, increase fruit size, etc.

Cytokinin is an organic, alkaline, purine derivative without nitrogen. It increases cell division, promotes lateral dominance (opposite to auxin), etc. Artificial auxin, gibberellin, and cytokinins are applied in agriculture.

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Chapter 1 Response And Chemical Co-Ordination In Plants Hormones Long Answer Type Questions

Question 1. Mention the common functions of Phytohormones in a plant body.

Answer:

Functions of phytohormones in a plant body

The functions of phytohormones in regulating different physiological activities in a plant are mentioned below.

1. Apical and lateral growth:

Primary growth of any plant occurs at the apex of stem and root This growth makes the shoot taller and the roots longer. Besides this, lateral meristem grows to make the plant body wider.

In both cases, phytohormones play an important role in instigating cell division in the growing regions.

2. Blooming of flowers:

Flower is the reproductive organ of a plant. It develops from floral buds. Phytohormones play a vital role in developing floral buds and blooming of flowers.

3. Caulogenesis and rhizogenesis:

Caulogenesis and histogenesis mean the formation of stem and root respectively. Phytohormones promote the development of stem from plumule and root from radical.

4. Germination of seedte:

Seeds remain dormant for a certain period after its formation. In the presence of certain external and internal factors, seeds come out of this dormant state and undergo germination.

Phytohormones activate certain enzymes and enhance the supply of food to the embryo to promote the germination process.

5. Tropic movement:

Phytohormones play a very important role in regulating growth-related movements of curvature, especially phototropic and geotropic movements in plants.

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Question 2. Mention the salient features of phytohormones.

Answer:

Salient features of phytohormones

The salient features of phytohormones are mentioned here.

1. Source:

Phytohormones are synthesized in the meristematic tissues of the apical region of stems and roots, tender leaves, plumule, radical, and other growing tissues.

2. Nature of transportation:

Phytohormones act close to their sources or away from it. These are carried to different target tissues by intercellular diffusion through the xylem and phloem.

3. Function:

Phytohormones regulate the growth of apical and lateral buds, blooming of flowers, formation of fruits and seeds, germination of seeds, budding, sensitivity, and delayed senescence.

4. Fate:

Hormones denature after their functions are over. Different hormones are broken down by the action of enzymes or by some other factors.

For example, auxin denatures by bright light and indole acetic acid oxidase enzyme. Gibberellin and cytokinin are also disintegrated by gibberellin oxidase and cytokinin oxidase respectively.

Question 3. Define auxin. Mention the silent features of auxin.

Answer:

The indole group containing, nitrogenous, acidic plant growth regulator, synthesized in the apical meristems, which flows downward and hastens the growth of plants is called auxin.

Salient features of auxin:

  1. Auxin is an important phytohormone which facilitates plant growth.
  2. It is an organic acid composed of carbon, hydrogen, nitrogen, and oxygen.
  3. Auxin is synthesized from an amino acid, named tryptophan.
  4. Auxin is produced in coleoptile, apical meristems of stem and root.
  5. It flows downward from the apical meristem of stems through the phloem. However, auxin from root tip cam, diffuse a little upward to reach the cells of the growing region of the root.
  6. Auxin moves away from the source of light and acts better in darkness and its transport is polar in nature.
  7. It is soluble in water and is diffused easily through the cell membrane.
  8. In the stem, a higher concentration of auxin promotes cell division but in the roots, a lower concentration of auxin helps in cell division.

 

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Question 4. Mention the role of auxin in the plant body.

Answer:

Role of auxin:

In plants, auxin plays important roles which are mentioned below.

1. Apical dominance:

By the action of auxin, apical buds grow quickly whereas, the growth of axillary buds is hindered. So, a plant becomes taller by the action of auxin. This is called apical dominance.

If the apex of a stem Is cut off, the axillary buds start to grow and the plant become a busby duo for branding.

WBBSE Solutions For Class 10 Life Science And Environment Chapter 1 Response And Chemical Co Ordination In Plants Hormones Role of auxin in plant body

 

2. Cell division and cell enlargement:

Auxin promotes DNA synthesis and thus, hastens cell division. By Ibis process, number of colls Increase In a growing region. Auxin delays the hardening of cell walls of young cells and lets them add to size and volume.

By the action of auxin, vacuoles grow Inside cells, which helps to enlarge cells.

3. Growth of fruit:

After fertilization, the auxin level elevates inside the ovary, which transforms the ovary Into a troll and ovules Into seeds. In some flowers, auxin level increases even before fertilization and the ovary grows to form fruit.

Without fertilization, the ovule cannot develop as a seed, therefore, these fruits grow up without any seed inside. Thus, auxin has a role in forming parthenocarpic or seedless fruits.

4. Growth of root:

bow concentration of auxin instigates cell division in the growing region of roots. Thus, auxin helps in the growth of the root system in plants.

A higher concentration of auxin, on the other hand, promotes the growth of adventitious roots from the nodes of stems.

5. Regulation of tropic movement:

Auxin plays an important role in controlling tropic movement in plants. Phototropic and geotropic movements occur under the direct control of auxin due to its unequal distribution.

Question 5. Explain the role of auxin In regulating phototropic and geotropic movement in plants.

Answer:

Role of auxin in regulating phototropic and geotropic movement in plants:

Auxin plays a very important role in regulating phototropic and geotropic movement in plants. Scientists Went and Cholodny experimentally proved that this phytohormone is a photophobic compound, that is, it gets accumulated away from the source of light.

Due to this nature, plant parts have unequal distribution of auxin. In the stem, concentrated auxin instigates cell division. Therefore, the cells of the stem, opposite to light, divide faster.

As a result, the stem bonds towards the source of light and is opposite to the source of gravity. Thus, the stem shows positive phototropism and negative geotropism.

Cells of roots, on the other hand, divide quickly in lower concentrations of auxin. Here, cell division occurs at a higher rate at that side which faces tile light. So, the root bends opposite to the source of light, that is, towards gravity.

Thus, it can be clearly established, that roots demonstrate negative phototropism and positive geotropism.

 

WBBSE Solutions For Class 10 Life Science And Environment Chapter 1 Response And Chemical Co Ordination In Plants Hormones Phototropic and geotropic movement in plants

 

Question 6. What is gibberellin? State the salient features of gibberellin.

Answer:

Gibberellin:

Gibberellin is a terpenoid type of non-nitrogenous, acidic phytohormone. Gibberellin is synthesised in cotyledons of matured seeds. It helps in breaking the dormancy of seeds and promoting their germination.

Salient features of gibberellin:

  1. Gibberellin is composed of carbon, hydrogen, and oxygen. It is a non-nitrogenous compound.
  2. It is an acidic compound belonging to the terpenoid group.
  3. It can flow through both xylem and phloem in upward and downward directions.
  4. It is soluble in water, hence, can diffuse into the tissues easily.
  5. The maximum amount of. gibberellin occurs in the cotyledons of seeds.

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Question 7. Name different types of gibberellins. State the role of gibberellin in plants. Part question, What influences gibberellin hormone exert on the seeds and internode of plants? Explain.

Answer:

Types of gibberellins:

The chemical name of gibberellin is gibberellic acid (GA). There are about 40 different types of gibberellins isolated from different plants. Some of the common types are GA3, GA7, GAp, etc.

Role of gibberellin in plants:

Gibberellins play different roles in the plant bodies, which are mentioned below.

WBBSE Solutions For Class 10 Life Science And Environment Chapter 1 Response And Chemical Co Ordination In Plants Hormones Role of gibberellin in internodal growth

 

1. Breaking dormancy of seed and bud:

For a certain period, the sign of life is not visible in seeds. This phase is called dormancy of seed. During dormant stage, seed contains less gibberellin.

Just before germination, the gibberellin level elevates in it. This phytohormone increases the activity of enzymes in the seed and helps in breaking its dormancy and facilitates germination.

2. Promoting growth of internodes:

Gibberellin increases the rate of cell division in the intercalary meristem. Due to this, the internodes of the stem increase in length, and thus, the overall height of the plant increases.

3. Increasing the size of the fruit:

Gibberellin quickens the growth of fruits and thus, increases their size. A synthetic form of gibberellin also helps in the formation of seedless or parthenocarpic fruits. Seedless tomatoes, apples, pears, grapes, etc. can be produced by gibberellin treatment.

4. Increasing the size of leaves and flowers:

Gibberellin enhances cell division to increase the size of leaves and flowers.

 

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Question 8. what is cytokinin? Mention the salient features of cytokinin.

Answer:

Cytokinin

The purine group containing, nitrogenous, basic phytohormone, produced in fruits and endosperm, at regulates the cell division process, is known as cytokinin.

Salient features of cytokinin

  1. Cytokinin is a nitrogenous basic organic compound.
  2. It is a compound belonging to purine group.
  3. It works in coordination with auxin.
  4. To reach the target tissue, it can move to any direction in the plant body. It can also act on its source as well.
  5. This phytohormone is highly soluble in water, hence, can diffuse into any tissue easily.
  6. It helps in cytokinesis of the plant cells, hence, termed as cytokinin.

Question 9. State the role of cytokinin in the plant body.

Answer:

Role of cytokinin in plant body:

Cytokinin plays an important role is the plant body. These are mentioned here.

1. Promoting cell division:

The main function of cytokinin is to bring about cytokinesis in plant cells. With the help of auxin, it helps in the synthesis of DNA during the S-phase of the cell cycle.

In this way, cytokinin helps in mitosis. It also plays role in the enlargement of newly divided cells.

2. Promoting growth of axillary buds:

Cytokinin promotes the development and growth of axillary buds. By this action, many branches develop in a plant and it becomes bushy.

3. Preventing shedding of leaves:

Due to degeneration of the tissues of the leaf base, a leaf is shed off. Cytokinin prevents degeneration of the tissues at the leaf base and thus, prevents early shedding of leaves.

4. Delaying senescence in plants:

Cytokinin holds up degeneration of nucleic acids and proteins within cells. It also assists in the synthesis of certain proteins. By this process, cytokinin helps to keep the cells alive for a longer period, thus delaying senescence in plants.

The flowers of a bouquet or flower vase are sprayed with cytokinin to keep them fresh for a longer time.

5. Preventing apical dominance:

Cytokinin prevents the free growth of apical bud. By this action, it prevents a plant to become markedly tall.

Question 10. Explain any four roles of synthetic hormones. Part question, Analyse the role of synthetic plant hormones in increasing the production and solving the problem of weeds in agriculture.

Answer:

Role of synthetic hormones:

Synthetic hormones are successfully used in agriculture and horticulture. The roles of these synthetic hormones are mentioned below.

1. Developing new plants from stem cuttings:

Cuttings are used for artificial vegetative propagation of different plants like roses, Hibiscus, marigold, Chrysanthemum, ‘etc. After cutting the twigs from a mother plant, a solution of synthetic auxin or auxin powder is applied at the cut end.

Then, these cuttings are planted in moistened soil. By the action of this hormone, adventitious roots grow from the cut end and the cutting grows as an individual daughter plant.

2. Preventing shedding of immature fruits:

Sometimes, immature fruits shed off from the plant if these plants are sprayed with synthetic auxin solution for a few times during ear y developmental phase of the fruits, the rate of immature shedding declines sharply.

Horticulturists spray auxin solution on mango, litchi, grapes, banana, and several other fruit plants to prevent immature shedding of fruits. Synthetic gibberellin and synthetic cytokinin are also effective.

3. Destroying weeds:

Weeds growing in the crop fields share water and nutrients with agricultural crops. This affects the quality of production. Scientists have revealed that the application of certain phytohormones destroys the dicotyledonous herbs and shrubs.

Application of a synthetic auxin named 2, 4-D effectively kills dicotyledonous weeds from monocot crop (paddy, wheat, etc.) fields.

4. Production of parthenocarpic fruits:

Fruits, produced from the ovary without fertilization do not contain seeds and become larger. These are called parthenocarpic fruits. A treatment of auxin solution before the maturation of flowers triggers the development of the ovary.

As a result, seedless fruits are produced before fertilisation. Synthetic auxin is successfully applied on the plants of guava, grapes, banana, watermelon, etc. to produce seedless fruits.

Synthetic gibberellin is comparatively more effective on tomato plants. These two synthetic phytohormones are used to produce parthenocarpic fruits.

wbbse class 10 life science question answer

Question 11. Compare among auxin, gibberellin, and cytokinin.

Answer:

Comparison among auxin, gibberellin, and cytokinin

WBBSE Solutions For Class 10 Life Science And Environment Chapter 1 Sensitivity And Response In Plants Comparison among Auxin, Gibberellin and Cytokinin

 

Chapter 1 Response And Chemical Co-Ordination In Plants Hormones SAQs

Question 1. What is a hormone?
Answer:

Hormone:

Hormone is a biochemical compound, produced in some typical cluster of cells or within endocrine glands.

Hormones are transported to specific target organs or tissues through body fluids to coordinate different physiological reactions and it denatures after completing its function.

Question 2. Mention the importance of hormones in plants.
Answer:

The importance of hormones in plants:

With maturity, different tissues grow within the plant body to develop structural and functional complexities in it. Phytohormones or plant hormones are necessary for this growth and thus, they act as growth regulators.

These hormones also coordinate and regulate different physiological activities in various tissues.

Question 3. Why are hormones called ‘chemical messenger?
Answer:

Hormones called ‘chemical messenger:

All hormones are biochemical substances, that regulate various physiological activities in plants and animals. These biochemical substance acts on a specific organ or tissue away from its site of origin to perform their respective functions. Therefore, hormones are called ‘chemical messengers.

wbbse class 10 life science question answer

Question 4. Why are hormones called the growth regulators of plants?
Answer:

In plants, hormones regulate the growth of different tissues and growth-related movements. Different phytohormones regulate the growth of apical, lateral and intercalary meristem and tropic movement of plants.

Therefore, hormones are called growth regulators of plants.

Question 5. Write down the chemical name and chemical nature of auxin.
Answer:

Chemical name of auxin is Indole Acetic Acid. Chemically, auxin is an organic acid composed of carbon, hydrogen, oxygen and nitrogen.

Question 6. Why does the root bend away from the light?
Answer:

The root bend away from the light:

The growth of plants is mainly controlled by the uneven distribution of auxin hormone. Auxin gets accumulated at higher concentration in the cells opposite to the light source. Cells of the root are more sensitive in lower concentrations of auxin.

In the root, the cells on the side adjacent to the light source have less amount of auxin. For this reason, these cells are divided more rapidly and the root bends away from the light.

Question 7. Mention the site of secretion and target tissues of auxin.
Answer:

Site of secretion:

Auxin is secreted from the apical meristem of the root and stem, coleoptile, tender leaves, etc.

Target tissues:

Auxin moves from its site of secretion to reach its target organs, i.e., meristem- Matic tissues of different growing organs by diffusion and initiates cell division.

wbbse class 10 life science question answer

WBBSE Solutions For Class 10 Life Science And Environment Chapter 1 Response And Chemical Co Ordination In Plants Hormones Apical meristem of stem

Question 8. What is parthenocarpy? Name a phytohormone helping in this process.

Answer:

Parthenocarpy:

The process by which the ovary of a flower develops into a fruit without fertilization within the ovule is called parthenocarpy.

 

WBBSE Solutions For Class 10 Life Science And Environment Chapter 1 Response And Chemical Co Ordination In Plants Hormones Seedless fruits

 

Phytohormone helping in parthenocarpy:

Auxin helps in parthenocarpy. By this process, watermelon, lemon and many other fruits can be produced without the formation of seeds.

Question 9. Parthenocarpy is not applicable in cashew nuts, pomegranates, etc.—explain.

Answer:

Parthenocarpy is not applicable in cashew nuts, pomegranates, etc:

Through parthenocarpy, seedless fruit is formed from the ovary without fertilization. In cashew nut or pomegranate, the seed is edible.

Parthenocarpy will produce seedless fruit which is of no use in these cases. So parthenocarpy is not applicable in these fruits.

Question 10. What are the importance of parthenocarpy in horticulture?

Answer:

The importance of parthenocarpy in horticulture are mentioned below.

Parthenocarpy produces seedless fruit which are easy to eat and easily digestible.

In some fruit, seeds contain components which degrade fruit very first. In Parthenocarpic fruit due to the absence of seed fruits will remain fresh for a long time.

Question 11. Write ” the names of a natural and two Synthetic auxins

Answer:

The name of a natural auxin is Indole Acetic Acid (IAA).

The name of two synthetic auxins are Indole Propionic Acid (IPA) and Indole Butyric Acid (IBA).

Question 12. What does dormancy of seed mean? Which phytohormone helps in breaking the dormancy of seeds?

Answer:

Dormancy of seed:

Delaying of germination of seeds even in optimum environmental conditions, due to an extremely slowed down rate of metabolic activities, is known as dormancy of seed.

Phytohrmone helping in breaking seed dormancy:

Gibberellin is the phytohormone, which helps in breaking the dormancy of seeds.

Question 13. Mention two sources and two functions of cytokinin.

Answer:

Sources: Two sources of cytokinin are—

  1. The endosperm of maize and
  2. Coconut water.

Functions:

Two functions of cytokinin are as follows—

  1. It helps in cell division.
  2. It de ays the shedding of leaves.

Wbbse Class 10 Life Science Solutions

Question 14. Write down the chemical name and chemical nature of cytokinin.

Answer:

  1. The chemical name of cytokinin is 6-furfuryl aminopurine.
  2. Cytokine is an alkaline, organic penne derivative with carbon, hydrogen, and oxygen-nitrogen.

Question 15. What will happen, if you forget to apply cytokinin in a plant tissue culture medium?

Answer:

Cytokinin helps in the cell division process. If cytokinin is not added to a plant tissue culture medium, cell division will not take place, as the cell will not undergo mitosis. As a result, tissue growth will be hampered.

Question 16. Why does a plant become bushy if its apex is cut off?

Answer:

Maximum auxin is produced in the apical meristem to maintain the apical dominance of a plant. If the apex of the stem is cut off, the supply of auxin decreases.

This situation stops apical dominance and allows axillary buds to grow faster to make the plant bushy.

Question 17. Which phytohormones a horticulturist may apply to his apple garden to get a bigger size of fruits and to delay the marketing process to get a better price?

Answer:

To get a bigger size of apples, a horticulturist should spray gibberellin to the apples of his garden. To keep the fruits fresh for a longer time for delayed marketing process, ‘he should apply cytokinin.

Question 18. What is a synthetic hormone?

Answer:

Synthetic hormone:

Scientists have synthesized certain chemicals in laboratories, which have similar chemical and functional properties to that of natural phytohormones. These are known as synthetic hormones.

For example—Indole propionic Acid, indole butyric acid, naphthalene acetic acid, etc. are a few synthetic phytohormones.

Question 19. Several weeds have grown in your school ground. Which phytohormone will you apply to destroy it?

Answer:

Auxin acts as a good weedicide. application of auxin in proper does may kill the dicotyledonous weeds. Therefore we shall spray auxin solution like the synthetic auxin, 2,4-D on the weeds to destroy them.

Question 20. What does postulated hormone mean?

Answer:

Postulated hormone:

Chemical natures of certain phytohormones are yet to be known, though the scientists know their functions. These phytohormones are known as postulated hormones.

Example—Florigen is a post-dated phytohormone, which is believed to instigate the blooming of flowers.

 

Chapter 1 Response And Chemical Co-Ordination In Plants Hormones MCQs

Question 1. The term ‘hormone’ was coined by—

  1. Bayliss and Starling
  2. Kurosawa
  3. Went
  4. Sir Jagadish Chandra Bose

Answer: 1. Bayliss and Starling

Question 2. The hormone is a/an—

  1. Enzyme
  2. Receptor
  3. Physical co-ordinator
  4. Chemical co-ordinator

Answer: 4. Chemical co-ordinator

Wbbse Class 10 Life Science Solutions

Question 3. An example of a natural hormone is—

  1. Auxin
  2. IPA
  3. NAA
  4. IBA

Answer: 1. Auxin

Question 4. A synthetic hormone is—

  1. IAA
  2. NAA
  3. GA
  4. Cytokinin

Answer: 2. NAA

Question 5. A gaseous hormone is—

  1. Auxin
  2. IPA
  3. Dormin
  4. Ethylene

Answer: 4. Ethylene

Question 6. An experiment with auxin was done for the first time on—

  1. Pea plant
  2. Wheat plant
  3. Paddy plant
  4. Oat plant

Answer: 4. Oat plant

Question 7. Which of the following performs chemical co-ordination in a living organism?

  1. Vitamin
  2. Enzyme
  3. Hormone
  4. Pheromone

Answer: 3. Hormone

Question 8. Florigen is a type of—

  1. Plant hormone
  2. Animal hormone
  3. Enzyme
  4. Vitamin

Answer: 1. Plant hormone

Question 9. Which of the following is available in coleoptiles?

  1. Gibberellin
  2. Cytokinin
  3. Auxin
  4. Florigen

Answer: 3. Auxin

Question 10. A non-nitrogenous plant hormone is—

  1. Gibberellin
  2. Cytokinin
  3. Auxin
  4. All of these

Answer: 1. Gibberellin

 

Wbbse Class 10 Life Science Solutions

Question 11. Which of the following helps to produce seedless fruits?

  1. Ethylene
  2. Auxin
  3. Florigen
  4. All of these

Answer: 2. Auxin

Question 12. The plant hormone that helps to keep a cut-off leaf fresh for some days—

  1. Auxin
  2. GA
  3. Cytokinin
  4. IPA

Answer: 3. Cytokinin

Question 13. The flow of auxin within a plant is—

  1. Upward
  2. Downward
  3. Lateral
  4. In all directions

Answer: 2. Downward

Question 14. The flow of gibberellins within the plant body is—

  1. Upward
  2. Downward
  3. Both A and B
  4. Lateral

Answer: 3. Both A and B

Question 15. The hormone capable of Increasing the height of a plant by eliminating its hereditary dwarfness is—

  1. Auxin
  2. Gibberellin
  3. Cytokinin
  4. Florigen

Answer: 2. Gibbereilin

Question 16. Gibberellin belongs to—

  1. Purine group
  2. Indole group
  3. Pyrimidine group
  4. Terpenoid group

Answer: 4. Terpenoid group

Question 17. Chemical components of gibberellin are—

  1. Carbon, hydrogen, oxygen, and nitrogen
  2. Carbon, hydrogen, and oxygen
  3. Carbon, hydrogen, nitrogen, and sulphur
  4. Carbon, sulphur, and phosphorus

Answer: 2. Carbon, hydrogen and oxygen

Wbbse Class 10 Life Science Solutions

Question 18. The phytohormone available in coconut water, the endosperm of maize, and wheat is—

  1. Auxin
  2. Gibberellin
  3. Cytokinin
  4. IBA

Answer: 3. Cytokinin

Question 19. Cytokinin works better in the presence of—

  1. Gibberellin
  2. Ethylene
  3. Auxin
  4. Abscisic acid

Answer: 3. Auxin

Question 20. The hormone helping in cell division of plant cells is—

  1. Florigen
  2. Oxytocin
  3. Ethylene
  4. Cytokinin

Answer: 4. Cytokinin

Question 21. The hormone that breaks the dormancy of seeds and buds is—

  1. Auxin
  2. Gibberellin
  3. Cytokinin
  4. Ethylene

Answer: 2. Gibbereilin

Question 22. The hormone that plays an important role in controlling phototropic and geotropic movement in plants is—

  1. Auxin
  2. Ethylene
  3. Cytokinin
  4. Florigen

Answer: 1. Auxin

Question 23. The term ‘auxin’ was coined by—

  1. Went
  2. Sir Jagadish Chandra Bose
  3. Pavlov
  4. Schwann

Answer: 1. Went

Question 24. The process of formation of seedless fruits without fertilization is called—

  1. Parthenogenesis
  2. Parthenocarpy
  3. Apogamy
  4. Apospory

Answer: 2. Parthenocarpy

Question 25. The phytohormone helping in the synthesis of a-amylase is—

  1. Cytokinin
  2. Auxin
  3. Gibberellin
  4. Ethylene

Answer: 3. Gibbereilin

Question 26. The main cytokinin is—

  1. Zeatin and kinetin
  2. 2, 4-D
  3. GA3 and GA7
  4. 2, 4, 5-T

Answer: 1. Zeatin and kinetin

Question 27. The hormone that helps in growing roots from cutting is—

  1. Artificial GA
  2. Artificial cytokinin
  3. Artificial auxin
  4. Ethylene

Answer: 3. Artificial auxin

Wbbse Class 10 Life Science Solutions

Question 28. Which of the following is a nitrogenous acidic plant hormone?

  1. Auxin
  2. Aldosterone
  3. Oxytocin
  4. Ethylene

Answer: 1. Auxin

Question 29. Which of the following is produced in the apical meristem of plants?

  1. Auxin
  2. Cytokinin
  3. Florigen
  4. Gibberellin

Answer: 1. Auxin

Question 30. The amino acid from which auxin is synthesized is—

  1. Tryptophan
  2. Tyrosine
  3. Valine
  4. Lysine

Answer: 1. Tryptophan

Question 31. A postulated phytohormone is—

  1. Auxin
  2. IPA
  3. Florigen
  4. Ethylene

Answer: 3. Florigen

Question 32. Which of the following is a nitrogenous plant hormone that is basic in nature?

  1. Auxin
  2. Cytokinin
  3. Vasopressin,
  4. Thyroxine

Answer: 2. Cytokinin

Question 33. Which of the following postpones the shedding of leaves?

  1. Auxin
  2. Gibberellin
  3. Cytokinin
  4. Florigen

Answer: 3. Cytokinin

Question 34. Gibberellin was discovered by—

  1. Eiichi Kurosawa
  2. Teijiro Yabuta
  3. Ronald Ross
  4. Fredrick Sanger

Answer: 1. Eiichi Kurosawa

Question 35. Gibberellin was isolated and named by—

  1. Eiichi Kurosawa
  2. Teijiro Yabuta
  3. Kawasaki
  4. Bayliss and Starling

Answer: 2. Teijiro Yabuta

Question 36. Gibberella fujikurol is a

  1. Fungus
  2. Bacterium
  3. Alga
  4. Moss

Answer: 1. Fungus

Question 37. Which of the following hormone shows the Richmond-Lang effect?

  1. Auxin
  2. Gibberellin
  3. Cytokinin
  4. Florigen

Answer: 3. Cytokinin

Question 38. Which of the following hormone expands the cell size?

  1. Auxin
  2. Gibberellin
  3. Cytokinin
  4. Ethylene

Answer: 1. Auxin

 

Chapter 1 Response And Chemical Co-Ordination In Plants Hormones VSAQs

Question 1. Name the substance responsible for controlling sensitivity and response in plants.
Answer: Hormone

Question 2. What is the meaning of the term ‘hormone’?
Answer: The term ‘hormone’ means ‘to stimulate’ or ‘to set in motion’.

Question 3. Mention the chemical nature of hormones.
Answer: Hormones are either proteins, steroids, amino compounds or organic acids.

Question 4. Name two growth regulators of plants.
Answer: Auxin and gibberellin

Question 5. Name an acidic plant hormone that contains a terpenoid group.
Answer: Gibberellin

Question 6. Mention the empirical formula of the chief gibberellin (GA3).
Answer: C19H22O6

Question 7. Write down the empirical formula of cytokinin.
Answer: C10H9N5O

Question 8. Which is the primary source of gibberellin?
Answer: Matured seed

Question 9. From which compound is cytokinin synthe¬sised chemically?
Answer: Cytokinin is synthesized chemically from adenine, a purine base.

Question 10. Which plant tissues carry gibberellin?
Answer: Xylem and phloem carry gibberellin in both downward and upward directions.

Question 11. Name a plant hormone that hinders plant growth.

Or,

Name a growth-retardant or growth-limiting plant hormone.
Answer: Abscisic acid (ABA) ‘

Wbbse Class 10 Life Science Solutions

Question 12. Mention the empirical formula of auxin.
Answer: C10H9O2N

Question 13. What is the chemical name of gibberellin?
Answer: Gibberellic acid

Question 14. Which phytohormone is available in matured seeds and cotyledons?
Answer: Gibberellin

Question 15. Which phytohormone promotes the growth of axillary buds to give the plant a bushy look?
Answer: Cytokinin

Question 16. Which phytohormone helps in the apical and lateral growth of a plant?
Answer: Auxin

Question 17. Which synthetic phytohormone is applied to grow roots from the cuttings of roses, Hibiscus, etc.?
Answer: Synthetic auxin

Question 18. By which process are seedless fruits produced hy applying phytohormone?
Answer: Parthenocarpy

Question 19. What Is the full form of IAA?
Answer: Indole Acetic Acid

Question 20. What is the full form of NAA?
Answer: Naphthalene Acetic Acid

Question 21. What is the full form of IPA?
Answer: Indole Propionic Acid

Question 22. What Is the full form of GA?
Answer: Gibberellic Acid

Question 23. Why Is abscisic acid called anti-gibberellin?
Answer: The action of abscisic acid is just opposite to that of gibberellin, so it is called anti-gibberellin.

Question 24. Name the predominant natural gibberellin.
Answer: GA

Question 25. Which phytohormone instigates the growth of internodes?
Answer: Gibberellin

Question 26. Which hormone helps in increasing the size and number of fruits?
Answer: Gibberellin

Question 27. Which hormone Is sprayed on the flowers of the bouquet to keep It fresh for a longer time?
Answer: Cytokinin

Question 28. Which phytohormone holds up the senescence of plants?
Answer: Cytokinin

Wbbse Class 10 Life Science Solutions

Question 29. Write the full form of 2,4-D.
Answer: 2,4-Dichlorophenoxy acetic acid

Question 30. Write the full form of 2,4,5-T,
Answer: 2,4,5-Trichlorophenoxy acetic acid

Question 31. From which compound auxin is synthesized chemically?
Answer: Auxin is synthesized chemically from an amino acid tryptophan.

Question 32. Give one example of synthetic cytokinin.
Answer: Benzyl Amino Purine (BAP)

 

Chapter 1 Response And Chemical Co-Ordination In Plants Hormones Fill In The Blanks

Question 1. The main growth, regulating, and growth-promoting substance of a plant is ________.
Answer: Hormone

Question 2. The main co-ordinating substance in a plant body is ________.
Answer: Hormone

Question 3. The growth of a plant due to cell division in apical meristem is called ________ growth.
Answer: Primary

Question 4. By ________ growth, a plant increases in diameter.
Answer: Secondary

Question 5. The first discovered plant hormone is ________.
Answer: Auxin

Question 6. ________ is the main growth regulator of plants.
Answer: Auxin

Question 7. Auxin helps In the growth of ________ buds.
Answer: Apical

Question 8. A lower concentration of auxin promotes the growth of ________.
Answer: Root

Question 9. Gibberellin promotes the cell division in ________ meristem to increase the height of a stem.
Answer: Intercalary

Question 10. ________ hormone acts opposite to auxin.
Answer: Cytokinin

Question 11. Seedless watermelon is an example of ________ fruit.
Answer: Parthenocarpic

Wbbse Class 10 Life Science Solutions

Question 12. Auxin helps in the formation of ________ which results in the secondary growth of plants.
Answer: Cambium

Question 13. ________ helps in the blooming of flowers in plants.
Answer: Florigen

Question 14. A gaseous hormone, named ________, helps in the ripening of fruits.
Answer: Ethylene

Question 15. Cytokinesis is hastened in plant cells by the action of ________ hormone.
Answer: Cytokinin

Question 16. Cell division in the growing regions of a plant body is initiated by ________ hormone.
Answer: Auxius

Question 17. The concentration of ________ hormone increases in the ovary after pollination and fertilis¬ation in the flower.
Answer: Auxis

Question 18. Cytokinin is composed of ________ type of nitrogenous base.
Answer: Purine

Question 19. Application of ________ prevents the shedding of immature fruit.
Answer: Auxin

Question 20. ________ is an example of an artificial weedicide hormone.
Answer: 2,4-D

 

Chapter 1 Response And Chemical Co-Ordination In Plants Hormones State True or False

Question 1. Ethylene was discovered and extracted from a fungus named Gibberella fujikuroi.
Answer: False

Question 2. Cytokinin delays the shedding of immature leaves.
Answer: True

Question 3. The tropic movement of plants is controlled by gibberellin.
Answer: False

Question 4. Hormones are denatured after its function is over.
Answer: True

Question 5. Auxin promotes apical dominance.
Answer: True

Question 6. Gibberellin is available in matured seeds.
Answer: True

Question 7. Cytokinin plays an important role in the internodal growth of plants.
Answer: True

Question 8. Cytokinin is also known as kinin.
Answer: False

Question 9. Gibberellin hormone prevents the immature shedding of leaf of plants.
Answer: False

Question 10. Artificial hormones are also known as plant growth regulators.
Answer: True

Question 11. Florigen helps in information of fruits.
Answer: False

 

Chapter 1 Response And Chemical Co-Ordination In Plants Hormones Match The Columns

1.

WBBSE Solutions For Class 10 Life Science And Environment Chapter 1 Sensitivity And Response In Plants Match the columns 1

Answer: 1. C, 2. E, 3. D, 4. B, 5. A, 6. G

2.

WBBSE Solutions For Class 10 Life Science And Environment Chapter 1 Sensitivity And Response In Plants Match the columns 2

Answer: 1. D, 2. A, 3. G, 4. E, 5. C, 6. B

3.

WBBSE Solutions For Class 10 Life Science And Environment Chapter 1 Sensitivity And Response In Plants Match the columns 3

Answer: 1. C, 2. D, 3. F, 4. B, 5. A, 6. E

4.

WBBSE Solutions For Class 10 Life Science And Environment Chapter 1 Sensitivity And Response In Plants Match the columns 4

Answer: 1. B, 2. D, 3. A, 4. G, 5. F, 6. C

 

Chapter 1 Response And Chemical Co-Ordination In Plants Hormones Find The Odd One Out

Question 1. IBA, GA, JPA, 2,4-D
Answer: GA

Question 2. IAA, GA, IBA, ABA
Answer:IBA

Question 3. Promotion of cell division, Preventing apical dominance by initiating the growth of lateral buds, Ripening of fruits, Delaying senescence
Answer: Ripening of fruits

Question 4. Promotion of cell division, Prevention of shedding of immature fruits, Widening of leaves, Developing adventitious roots from stem cuttings
Answer: Widening of leaves

Question 5. Auxin, Oxytocin, Gibberellin, Cytokinin
Answer: Oxytocin

Question 6. Apical dominance, Parthenocarpy, Tropic movement, Breaking of seed dormancy
Answer: Breaking of speed dormancy

Question 7. 2,4-Dichlorophenoxyaceticacid,Napthalene acetic acid, Indole acetic acid, Abscisic acid
Answer: Abscisic acid

Chapter 1 Response And Chemical Co-Ordination In Plants Hormones Fill In The Blanks By Looking At The First Pair

Question 1. Gibberellin: Carbon, hydrogen, and oxygen:: Auxin: _________
Answer: Carbon, Hydrogen, Oxygen, and nitrogen

Question 2. Gibberella fuzikuroi : Gibberellin :: Coconut water: _________
Answer: Cytokinin

Question 3. Promotion of cell division: Cytokinin:: Elongation of internodes: _________
Answer: Gibberellin

Question 4. Promotion of lateral branching: Cytokinin :: Apical dominance: _________
Answer: Auxis

Question 5. The lesser concentration of auxin: Faster growth of roots:: Higher concentration of auxin: _________
Answer: Faster growth stem

Question 6. Promotion of growth of adventitious roots from stem cuttings: Auxin :: Elongation of internodes: _________
Answer: Gibberellin

Question 7. Parthenocarpy: Auxin:: Delaying shedding of leaves: _________
Answer: Cytokinin

Question 8. Formation of parthenocarpic fruit: BB:: Destruction of weeds: _________
Answer: 2, 4-D

Question 9. Breaking dormancy of seeds: Gibberellic acid:: Tropic movement in plants: _________
Answer: Indole acetic acid

Question 10. Richmond-Lang effect : Cytokinin:: Apical dominance: _________
Answer: Auxin

Question 11. Cell division: Auxin:: Seed germination: _________
Gibberellin

Question 12. Auxis: Meristem:: Gibberellin: _________
Answer: Seed

 

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