Detailed explanations in West Bengal Board Class 10 Life Science Book Solutions Chapter 1B Response and Chemical Coordination in Plant Hormones offer valuable context and analysis.
WBBSE Class 10 Life Science Chapter 1B Question Answer – Response and Chemical Coordination in Plant Hormones
Short Answer Type Questions Marks : 2
Question 1.
What are plant hormones?
Answer:
Plant hormones of phytohormones are naturally-occurring organic substances used as chemical coordinators in plants. These are synthesized in one part of the plant body (in minute quantities) and are translocated to other parts when required. The five major types of phytohormones are :
- Auxins promote : cell division, bending of shoot towards the sources of light.
- Gibberellins : stimulate stem elongation.
- Cytokinins : promotes cell division.
- Abscisic Acid : inhibit growth, closing of stomate seed dormancy.
- Ethylene (gas hormone) : promotes full ripening and growth.
Question 2.
Name any two synthetic Auxins and mention one application for each.
Answer:
IAA : Induces root form and production of parthenocarpic fruit.
24D : Weedicide.
Question 3.
Mention any four physiological effects of Auxin.
Answer:
Induces cell division, induces apical dominance, induces root initiation, presents abscission.
Question 4.
Mention any four physiological effects of Gibberellins.
Answer:
Promotes internodal elongation, induces Parthenocarpic development of fruits, breaks dormancy in seeds.
Question 5.
Mention any four physiological effects of Cytokinins.
Answer:
Induces cell division, delay senescence, breaks dormancy, promotes growth of lateral root.
Question 6.
Classify the following phytohormones into growth promoters and growth inhibitors.
(a) Auxin
(b) Abscisic acid
(c) Cytokinin
(e) Ethylene.
Answer:
Growth promoters : Auxin, Cytokinin; Growth inhibitors: ABA, Ethylene.
Question 7.
What roles do synthetic Auxins play in tissue cultures?
Answer:
Induces cell division and organogenesis.
Question 8.
A plant becomes bushy, when its apical bud is removed. Why?
Answer:
When the apical bud is removed apical dominance is overcome and the lateral buds are induced to develop giving a bushy appearance to the plant.
Question 9.
How Gibberellins promote in seed germination?
Answer:
Gibberellins promote seed germination. Giberellins are weakly acidic growth hormones having ring structure, are synthesized in the apical shoot buds, root tips and developing seeds. During seed germination, especially of cereals Giberrellin stimulates the production of some messenger RNAs and then hydrolytic enzymes like amylases, lipases, proteases. The enzymes solubilize the reserve food of the seed.
Question 10.
Cut or excised leaves remain green for long if induced to root or dipped in Cytokinins. How?
Answer:
Cytokinins are plant growth hormones which are basic in nature. Cytokinins induce formation of new leaves, chloroplasts in leaves, which in turn keeps the leaves green for a longer duration of time. Cytokinins applied to marketed vegetables can keep them fresh for several days. Shelf life of cut shoot and flowers is prolonged by employing the hormones.
Question 11.
How Cytokinins hormone primarily helps in cell division?
Answer:
Cytokinin has a very specific effect on cell division (cytokinesis), hence the name Cytokinin. They contain kinetin and related compound generally called as kinins chemically, Cytokinins are degradation product of Adenine, ATP, NAD and NADP. Cytokinins are essential for cytokinesis though chromosome doubling can occur in their absence. Cytokinins bring about division even in permanent cells.
Question 12.
How Leaf fall can be prevented with the help of Cytokinins?
Answer:
Cytokinins delay senescence of leaves and other organs by mobilisation of nutrients. Its excessive presence stop protein and RNA synthesis in the leaves and hence stimulates their senescence.
Question 13.
How Gibberellins can replace vernalization?
Answer:
Gibberellin is a hormone that replaces vernalization. Vernalization is a period of cold treatment for plants, usually perennials or trees. Some plants won’t bloom without it. In vernilization plants are exposed to low temperature in order to stimulate flowering or to enhance seed production. The biennials form their vegetative body in the first year. Then they pass through a winter season and then produce flowers and fruits in the second year. By exogenous application of Gibberellins many biennials can be induced to behave as annuals and they no more require the natural chilling treatment for their flowering.
Question 14.
What do you means by nyctinastic leaf movements?
Answer:
It is a movement of leaves of many species from nearly horizontal leaves during the day and nearly vertical at night. These movements are controlled by biological clock, while the other conditions bending of shoot towards light, movement of root towards soil and movement of sunflower head tracking the sun are the conditions related to Auxins.
Question 15.
How abscisic acid controls leaf fall and dormancy?
Answer:
Before a leaf fall, a special zone of cells is formed at the base of the pedical or petiole. This zone is called as abscission zone. It is delimited by a protection layer on the stem side and a separation layer on the organ side. The leaf is ultimately separated and the phenomenon is abscission. ABA is also a growth inhibitor. It regulates the dormancy of seeds and buds perhaps by inhibiting the growth process. The ABA level decreases in the whole seed as their dormancy is broken.
Question 16.
What do you mean by Phytohormones?
Answer:
Growth hormones or phytohormones are defined as organic substances which are synthesized in minutes quantities in one part of the plant body and transported to another part where they influence specific physiological processes. Phytohormones are chemical substances which are synthesized by plants and are naturally occurring.
Question 17.
How Auxin concentration acts on the growing tips?
Answer:
Auxins are well known to promote elongation of stem and coleoptile. However when exogenous Auxin is given to intact plants this is not observed because the required amount of Auxin is already present in plants. When the apex of shoot is removed, then the exogenous application of Auxin promotes growth, this clearly indicates that growing apex, having meristematic cells, is the site where endogenous auxins are present in sufficient amount; once the apex is removed the source of Auxin is also removed.
Question 18.
Which chemical believed to be involved in flowering?
Answer:
Chailakhyan in 1937 gave the view that flower hormone namely Florigen is synthesized in the leaves under favourable photoperiodic conditions. This hormone is transmitted to the growing point where the flowering occurs.
Question 19.
Which hormone is responsible for apical dominance?
Answer:
Indole-3 Acetic Acid (IAA) is a natural Auxin which is responsible for apical dominance. In vascular plants especially the taller ones, if the apical bud is intact and growing, the lateral bud remains suppressed, removal of apical bud causes fast growth of lateral buds. This influence of apical bud in suppressing the growth of lateral buds is termed as apical dominance.
Question 20.
Write the function of Abscisic acid.
Answer:
Abscisic acid is hormone which is produced during adverse environmental condition. It also causes the closure of stomata under conditions of water stress as also under high concentration of CO, in the guard cells. Abscisic acid inhibits the K+ uptake by guard cells and promotes the leakage of malic acid. It results in reduction of osmotically active solutes so that the guard cells become flaccid and stomata get closed.
Question 21.
Bananas can be prevented from over-ripening by which process?
Answer:
In artificial ripening of banana, uncontrolled application of Ethylene gas may cause over ripening of banana. It can be prevented from over-ripening by dipping in Ascorbic acid solution.
Question 22.
Dwarfness can be controlled by treating the plant with Gibberellic acid. Explain.
Answer:
Giberellins help in the reversal of dwarfism in many genetically dwarf plants. External supply of Gibberellic acid causes rapid elongation of growth, e.g. Rosette plant of sugarbeet when treated with GA, undergoes marked longitudinal growth of axis.
Question 23.
The movement of Auxin is largely basipetal. Explain.
Answer:
Auxin is a growth promoting phytohormone. It moves mainly from the apical to the basal end (basipetally). This type of unidirectional transport is termed polar transport. Auxin is the only plant growth hormone known to be transported polarly. Recently it has been recognized that a significant amount of Auxin transport also occurs acropetally (from basal end to the apical end) in the root.
Question 24.
Gibberellic acid induces flower in long day plants under short day conditions. Explanation.
Answer:
Gibberellins are growth promoting phytohormones. Some of plants species flower only if the light period exceeds a critical length and others flower only if this period is shorter than some critical length. Gibberellins can substitute for the longday requirement in some species, showing an interaction with light.
Question 25.
Which plant hormone is used for inducing morphogenesis in plants tissue culture?
Answer:
Cytokinins are growth promoting phytohormones. Cytokinin plays an important part in organ formation (morphogenesis) with auxin. Different Auxin/Cytokinin ratio decides the development of root shoot ratio. The major physiological function of Cytokinins is to enhance cell division. If Cytokinin to Auxin ratio is low, then root formation takes place but if the ratio of Cytokinin to Auxin is high, then there is formation of meristematic cells in the callus.
Question 26.
How Gibberellins break the dormancy of potato tuber?
Answer:
Gibberellin is the hormone that breaks seed/but dormancy. The tubers of potato reproduce vegetatively to give house to new plants. So the dormancy of these tubers can be overcome by applying Gibberellin tubers.
Question 27.
How NAA prevents the fall of fruits?
Answer:
A-Naphthalene Acetic Acid (NAA) is a synthetic or exogenous Auxin. It prevents the formation of abscission layer, which is a layer of dead cells in the petiole and pedicel that causes fall of leaf or fruit. NAA prevents formation of this layer and so it prevents fall of leaf or fruit.
Question 28.
Coconut milk factor is Cytokinins. Explanation.
Answer:
Many experiments were done to sustain the proliferation of normal stem tissues in culture. The growth of culture was most dramatic when the liquid endosperm of coconut, also known as coconut milk, was added to the culture medium. This finding indicated that coconut milk contains a substance or substances that stimulate mature cells to enter and remain in the cell division cycle. Eventually coconut milk was shown to contain Cytokinin, Zeatin, but this finding was not obtained until several years after the discovery of the Cytokinins. The first Cytokinin to be discovered was the synthetic analogy kinetin.
Question 29.
How Gibberellins help in Cell elongation in internodal regions of the green plants?
Answer:
Gibberellins play a role in the elongation of internodes in ‘rosette’ plants. Before reproductive stage there is too much elongation of internodes but there is less leaf formation. An elongated internode without leaves is called a “bolt” like structure and the process is called “bolting”. Flowering takes place after bolting. Gibberellins induce cell division and cell elongation, when bolting takes place.
Question 30
How hormones can promote plan growth?
Answer:
Hormones can promote plant growth in two ways :
– Stimulating cell division in meristems to produce new cells.
Stimulating elongation in cells.
Question 31.
Why Cytokinin acts against Auxin?
Answer:
Cytokinin countracts apical dominance, prevents apical growth induced by Auxin. So, they acts against Auxin.
Question 32.
Give two examples of Auxin which are used in agriculture?
Answer:
(i) Early shedding of fruits and leaves are prevented.
(ii) Help in creating seedless fruit.
Question 33.
What is antiauxin?
Answer:
Cytokinin counteracts apical dominance, prevents apical growth induced by auxin, so they are also called antiauxin.
Question 34.
Name one Phytohormones. Mention one function of Auxin.
Answer:
Auxin is a Phytohormones.
Function : Root growth : Auxin promotes root growth only at extremely low concentrations.
Question 35.
Write two functions of Cytokinin?
Answer:
Two functions of Cytokinin :
(i) Promotes cell division : It is mainly concerned with the cytokinosis process of cell division.
(ii) Delay leaf senescence : Richmond and Long showed that kinetin delays senescence of leaves by retention of chlorophyl. It prevents drainage of nutrients from mature leaves.
Question 36.
What is parthenocarpy?
Answer:
Development of progenies from ovum without fertilization by sperm is known as parthenocarpy. eg. beas, wasp.
Question 37.
Mention two differences between plant and animal hormone.
Answer:
Plant hormone | Animal hormone |
i. Source-apical meristems of stem and root, coleoptile, endosperm, cotyledons etc. | i. Source-Endocrine glands. |
ii. They are transported through conducting system from their place of synthesis. | ii. Hormone is transported via blood and lymph. |
Long Answer Type Questions : 5 Marks
Question 1.
How do Auxins promote the growth of a tendril around a support?
Answer:
When tendrils come in contact with any support, the part of the tendril in contact with the object does not grow as rapidly as the part of the tendril away from the object. This is caused by the action of Auxin hormone. Less Auxin occurs on the side of contact as compared to the free side, as a result Auxin promotes growth on the free side and the tendrils coil around the support.
Question 2.
How does chemical coordination occur in plants?
Answer:
Chemical coordination occurs in plants with the help of plant hormones. Different plant hormones help to coordinate growth, development, and responss to the environment. They are synthesized at places away from where they act and diffuse to the area for action, for example, Auxin promotes cell growth, Gibberellins promote stem growth, Cytokinins promote cell division and Abscisic Acid inhibits growth and its effects include wilting of leaves.
Question 3.
Mention the sources of ‘Auxin’ hormone and two of its functions having practical application.
Answer:
The sources of ‘Auxin’ hormone :
- Growing apex of higher plants
- Organs like seeds, stem tips.
- In young expanding leaves.
The two functions of Auxin having practical application :
- Need eradication
- Parthenocarpic fruit development.
- Delay of senescence period.
Question 4.
Write the source and any two functions of Cytokinin.
Answer:
Source of Cytokinine :
- Fruits like apple, tomato, banana etc.
- Endosperm tissues.
- Found abundantly in coconut milk.
- Corn seed contains Cytokinin (Zeatin)
Functions (two) of Cytokinin :
- Cytokinin acts in presence of Auxin which induces cell division in plants.
- Cytokinin delays the senescence of leaves.
Question 5.
Write the full form of IBA. Define apical dominance.
Answer:
The full from of IBA is Indole Butyric Acid.
Apical Dominance : As a general rule, growth of the terminal shoot of a plant inhibits the development of lateral buds on the stem beneath. The inhibition is called apical dominance.
Multiple Choice Questions : 1 Mark
Question 1.
Which of the following is a plant hormone?
(a) Insulin
(b) Thyroxin
(c) Oestrogen
(d) Cytokinin
Answer:
(d) Cytokinin
Question 2.
Artifical ripening of fruit is carried out by
(a) Auxin
(b) Ethylene
(c) Abscisic acid (ABA)
(d) Gibberellin
Answer:
(b) Ethylene
Question 3.
Growth of the stem is controlled by
(a) Gibberellin
(b) Auxin
(c) Abscisic acid
(d) Cytokinin
Answer:
(a) Gibberellin
Question 4.
Which of the following synthetic hormones is used commercially for ripening fruits?
(a) IBA
(b) NAA
(c) BAP
(d) Ethephon
Answer:
(d) Ethephon
Question 5.
Choose the combination of hormones which cause bolting and apical dominance respectively.
(a) Auxin and Gibberellin
(b) Gibberellin and Auxin
(c) Auxin and Cytokinin
(d) Gibberellin and Ethylene
Answer:
(b) Gibberellin and Auxin
Question 6.
Maximum seed germination can be achieved by treating seeds with
(a) Auxin
(b) Gibberellin
(c) Abscisic acid
(d) Ethylene
Answer:
(b) Gibberellin
Question 7.
If a piece of sugarcane with nodes and internodes is placed in a beaker containing IBA, we can expect development of
(a) shoot
(b) roots
(c) leaf
(d) branch
Answer:
(b) roots
Question 8.
Match the hormones in column I with their physiological effects in column II and write the correct combinations.
Column I | Column II |
(a) Auxin | (p) fruit ripening |
(b) Gibberellin | (q) delay in senescence |
(c) Cytokinin | (r) apical dominance |
(d) Ethylene | (s) bolting |
(a) a = r, b = s, c = q, d = p
(b) a = r, b = q, c = s, d = p
(c) a = s, b = r, c = q, d = p
(d) a = r, b = s, c = p, d = q
Answer:
(a) a = r, b = s, c = q, d = p
Question 9.
Which of the following pertains to movement of plants?
(a) sleep movements
(b) phototropism
(c) gravitropism
(d) all of the choices are correct
Answer:
(d) all of the choices are correct
Question 10.
Which of the following ions are affected by Gibberellin and is also involved in signal transduction?
(a) H+
(b) Ca2+
(c) Na+
(d) Mg2+
Answer:
(b) Ca2+
Question 11.
Pinching the top off a plant to create fuller growth involves which of the following hormones?
(a) Auxin
(b) Ethylene
(c) Gibberellin
(d) Cytokinin
Answer:
(a) Auxin
Question 12.
The general sequence by which a plant responds to stimuli is
(a) Chloroplast-vascular bundle-sap
(b) Reception-transduction-response
(c) Sensory nerve-interneuron-motor nerve
(d) Input-reflex-output
Answer:
(b) Reception-transduction-response
Question 13.
Which of these terms refers to a growth of the plant towards light?
(a) Negative gravitropism
(b) Positive gravitropism
(c) Negative phototropism
(d) Positive phototropism
Answer:
(d) Positive phototropism
Question 14.
The response of roots growing downward is referred to as
(a) Negative gravitropism
(b) Positive gravitropism
(c) Thigmotropism
(d) Negative phototropism
Answer:
(b) Positive gravitropism
Question 15.
Pea vines twinning around a wire support is an example of
(a) Negative gravitropism
(b) Positive gravitropism
(c) Thigmotropism
(d) Negative phototropism
Answer:
(c) Thigmotropism
Question 16.
Plant hormones are generally produced in tissues.
(a) Cortical (cortex)
(b) Epidermal
(c) Meristem
(d) Vascular
Answer:
(c) Meristem
Question 17.
The Latin root words meaning “about” and “day” are the basis for the term
(a) Auxin
(b) Tropism
(c) Naștic
(d) Circadian
Answer:
(d) Circadian
Question 18.
Which statement about plant hormones is not true?
(a) Plant hormones include at least one form that is gas.
(b) Each naturally occurring hormone has a specific chemical structure.
(c) Hormones are among the principal internal regulators of plant growth.
(d) All known growth regulators of plant activities are chemicals produced naturally in plants.
Answer:
(d) All known growth regulators of plant activities are chemicals produced naturally in plants.
Question 19.
Which of these plant hormones is a growth inhibitor?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Gibberellin
Answer:
(a) Abscisic acid
Question 20.
Which of these plant hormones was studied in the 1880s by Charles and Francis Darwin in experiments on phototropism?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Ethylene
Answer:
(b) Auxin
Question 21.
Which plant hormone was discovered in infected rice seeding that grew extremely tall and slender?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Gibberellin
Answer:
(d) Gibberellin
Question 22.
Which plant hormone, developing in an apical bud, inhibits the growth of lower axillary buds?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Ethylene
Answer:
(b) Auxin
Question 23.
Indoleacetic acid (IAA) is the most commonly occurring form of which plant hormone?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Ethylene
Answer:
(b) Auxin
Question 24.
Dormancy in seeds and buds can be broken by application of which plant hormone?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Gibberellin
Answer:
(d) Gibberellin
Question 25.
A hormone that causes cell division and is found in coconut milk or in dividing root tissue is
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Ethylene
Answer:
(c) Cytokinin
Question 26.
Which of the following is/are an effect(s) of auxin?
(a) Applied to a woody cutting, it causes roots to develop
(b) Auxin production by seeds promotes the growth of fruit
(c) Trees sprayed with Auxin will keep mature fruit from falling to the ground
(d) All of the choices are the effect of Auxin.
Answer:
(d) All of the choices are the effect of Auxin.
Question 27.
How does Auxin actually work?
(a) In the presence of blue light, it triggers additional photosynthesis and growth
(b) In the presence of light, it increases the turgor pressure of the cell and accelerates growth
(c) In the presence of light, it increases the formation of hydrolytic enzymes that release energy needed for growth
(d) In the presence of unidirectional light, it moves to the shady side and activites an ATP-driven proton pump that result in weakened cell walls and eventual elongation.
Answer:
(d) In the presence of unidirectional light, it moves to the shady side and activites an ATP-driven proton pump that result in weakened cell walls and eventual elongation.
Question 28.
How does Gibberllin actually work?
(a) In the presence of blue light, it triggers additional photosynthesis and growth.
(b) In the presence of light, it increases the turgor pressure of the cell and accelerates growth.
(c) In the presence of light, it increases the formation of additional DNA that codes for additional plant structures.
(d) It attaches to a plasma membrane receptor and results in gene activation to produce the enzyme amylase that releases sugars for additional cell growth, division, and elongation.
Answer:
(d) It attaches to a plasma membrane receptor and results in gene activation to produce the enzyme amylase that releases sugars for additional cell growth, division, and elongation.
Question 29.
A chemical messenger from the embryo that apparently simulates a seed to digest the endosperm is
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Gibberellin
Answer:
(d) Gibberellin
Question 30.
Application of which hormone prevents plant tissues from senescing, or again?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Ethylene
Answer:
(c) Cytokinin
Question 31
Which plant hormone is a gas?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Ethylene
Answer:
(d) Ethylene
Question 32.
Which plant hormone stimulates the ripening of fruit and inhibits plant growth?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Ethylene
Answer:
(d) Ethylene
Question 33.
Which plant hormone is called the stress hormone because it produces dormancy in seeds and buds?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Ethylene
Answer:
(a) Abscisic acid
Question 34.
Which plant hormone is associated with the closure of the stomates in a plant under water stress?
(a) Abscisic acid
(b) Auxin
(c) Cytokinin
(d) Ethylene
Answer:
(a) Abscisic acid
Question 35.
Which statement is not correct about a circadian rhythm?
(a) These rhythms tend to persist even in the absence of daily light cues.
(b) An example is the opening of stomata in the morning and their closing at night.
(c) If plants are maintained in total darkness or total light, their circadian rhythm acts on a faster time scale.
(d) The primary usefulness of circadian rhythms seems to be to measure daylength changes so plants respond appropriately to seasonal environmental changes.
Answer:
(c) If plants are maintained in total darkness or total light, their circadian rhythm acts on a faster time scale.
Question 36.
Which is not a physiological change related to photoperiodism?
(a) Seed germination
(b) Root branching
(c) Breaking bud dormancy
(d) Some flowering
Answer:
(b) Root branching
Question 37.
The prayer plant, Maramta leuconeura, folds up its leaves each night in accordance with a circadian rhythm. If we were to ship this plant halfway around the world to a location where it is day time there, when it is might here, the plant will
(a) Slowly adjust to synchronize with the new day-night cycle
(b) Immediately switch to a new cycle and begin to open leaves in day and close them at night
(c) Detect the change but remain on its original cycle and therefore still fold leaves in day and open them at night
(d) Not detect the change and therefore remain on its original cycle.
Answer:
(a) Slowly adjust to synchronize with the new day-night cycle
Question 38.
Which statement is not true about photoperiodism?
(a) A short-day plant flowers, when the day length is shorter than some critical length
(b) A day-neutral plant flowers according to some form of regulation other than photoperiodism
(c) A long-day plant will flower even when the day period is not long enough if there is a short period of light during the dark period.
(d) The phytochrome from Pft is converted to Pr in daylight, producing the active from the induces flowering the long-day plants.
Answer:
(d) The phytochrome from Pft is converted to Pr in daylight, producing the active from the induces flowering the long-day plants.
Question 39.
The Greek root words meaning “plant” and “color” are the basis for the term
(a) Auxin
(b) tropism
(c) nastic
(d) phytochrome
Answer:
(d) phytochrome
Question 40.
How do some plants sees “know” when it is day and night, and perhaps when to germinate?
(a) They chemically count the circadian cycles.
(b) All plant hormones are products of photosynthetic systems.
(c) Photosynthetic rates provide direct evidence of sun-produced food.
(d) Phytochromes cycle between red and far-red absorption and light levels can inhibit germination.
Answer:
(d) Phytochromes cycle between red and far-red absorption and light levels can inhibit germination.
Question 41.
Gravitropism in roots
(a) is positive when plant roots grow downward
(b) is due to statoliths in the root cap cells
(c) is due to Auxins
(d) All of the choices are true.
Answer:
(d) All of the choices are true.
Question 42.
Apical dominance in plants is due to which of the following plants hormones?
(a) Ethylene
(b) Gibberellin
(c) Auxin
(d) Cytokinin
Answer:
(c) Auxin
Question 43.
Which of the following is/are true regarding Gibberellin?
(a) there are about 70 chemically different gibberellins
(b) are growth promoters causing stem elongation
(c) these hormones can break seed and bud dormancy
(d) all of the choices are true.
Answer:
(d) all of the choices are true.
Question 44.
Cytokinins
(a) are plant hormones that promote cell division
(b) are used in combination with Auxin to produce plants from undifferentiated callose tissue
(c) also work with oligosaccharins to effect tissue differentiation
(d) All of these are true regarding cytokinin
Answer:
(d) All of these are true regarding cytokinin
Question 45.
Gibberellin promotes
(a) seed germination
(b) seed dormancy
(c) leaf fall
(d) root elongation
Answer:
(a) seed germination
Question 46.
Cut or excised leaves remain green for long if induced to root or dipped in
(a) Gibberellin
(b) Cytokinin
(c) Auxin
(d) Ethylene
Answer:
(b) Cytokinin
Question 47.
Hormone primarily connected with cell division is
(a) IAA
(b) NAA
(c) Cytokinine
(d) Gibberellic acid
Answer:
(c) Cytokinine
Question 48.
Leaf fall can be prevented with the help of
(a) Abscisic acid
(b) Auxin
(c) Florigen
(d) Cytokinin
Answer:
(d) Cytokinin
Question 49.
Which of the following hormones can replace vernalisation?
(a) Auxin
(b) Cytokinin
(c) Gibberellin
(d) Ethylene
Answer:
(d) Ethylene
Question 50.
Which of the following movements is not related to Auxin level?
(a) bending of shoot towards light
(b) movement of root towards soil
(c) nyctinastic leaf movements
(d) movement of sunflower head tracking the sun
Answer:
(c) nyctinastic leaf movements
Question 51.
Phototropic and geotropic movements are linked to
(a) Gibberellin
(b) Enzymes
(c) Auxin
(d) Cytokinin
Answer:
(c) Auxin
Question 52.
Abscisic acid controls
(a) cell division
(b) leaf fall and dormancy
(c) shoot elongation
(d) cell elongation and wall formation
Answer:
(b) leaf fall and dormancy
Question 53.
Phytohormones are
(a) chemical regulation flowering
(b) chemical regulation secondary growth
(c) hormones regulating growth from seed to adulthood
(d) regulator synthesised by plants and influencing physiological processes.
Answer:
(d) regulator synthesised by plants and influencing physiological processes.
Question 54.
Highest Auxin concentration occurs
(a) in growing tips
(b) in leaves
(c) at base of plant organs
(d) in xylem and phloem
Answer:
(a) in growing tips
Question 55.
A chemical believed to be involved in flowering is
(a) Gibberellin
(b) kinetin
(c) Florigen
(d) IBA
Answer:
(c) Florigen
Question 56.
The hormone responsible for apical dominance is
(a) IAA
(b) GA
(c) ABA
(d) Florigen
Answer:
(a) IAA
Question 57.
Abscisic acid causes
(a) stomatal closure
(b) leaf expansion
(c) stem elongation
(d) root elongation
Answer:
(a) stomatal closure
Question 58.
Cytokinins
(a) promote abscission
(b) influence water movement
(c) photoperiod less than 12 hours, photoperiod below a critical length and uniterrupted long night
(d) short photoperiod and interrupted long night.
Answer:
(c) photoperiod less than 12 hours, photoperiod below a critical length and uniterrupted long night
Question 59.
Apical dominance is caused by
(a) Abscisic acid in lateral bud
(b) Cytokinin in leaf tip
(c) Gibberellin in lateral buds
(d) Auxin in shoot tip
Answer:
(d) Auxin in shoot tip
Question 60.
Bananas can be prevented from over-ripening by
(a) maintaining them at room temperature
(b) refrigeration
(c) dipping in ascorbic acid solution
(d) storing in a freezer
Answer:
(c) dipping in ascorbic acid solution
Question 61.
Dwarfness can be controlled by treating the plant with
(a) Cytokinin
(b) Gibberellin
(c) Auxin
(d) Antigibberellin
Answer:
(b) Gibberellin
Question 62.
The regulator which retards ageing/senescence of plant parts is
(a) Cytokinin
(b) Auxin
(c) Gibberellin
(d) Abscisic acid
Answer:
(a) Cytokinin
Question 63.
The movement of Auxin is largely
(a) centripetal
(b) basipetal
(c) acropetal
(d) both ‘a’ and ‘c’
Answer:
(b) basipetal
Question 64.
Gibberellic acid induces flower
(a) in short day plants under long day conditions
(b) in day-neutral plants under dark conditons
(c) in some gymnospermic plants only
(d) in long day plants under short day conditions
Answer:
(d) in long day plants under short day conditions
Question 65.
A plant hormone used for inducing morphogenesis in plant tissue culture is
(a) Cytokinin
(b) Ethylene
(c) Abscisic acid
(d) Gibberellin
Answer:
(a) Cytokinin
Question 66.
Which hormone breaks dormancy of potato tuber?
(a) Gibberellin
(b) IAA
(c) ABA
(d) Zeatin
Answer:
(a) Gibberellin
Question 67.
Which of the following prevents the fall or fruits?
(a) GA
(b) NAA
(c) Ethylene
(d) Zeatin
Answer:
(b) NAA
Question 68.
Coconut milk factor is
(a) an Auxin
(b) a Gibberellin
(c) Abscisic acid
(d) Cytokinin
Answer:
(d) Cytokinin
Question 69.
Cell elongation in internodal regions of the green plants takes place due to
(a) Indole Acetic Acid
(b) Cytokinin
(c) Gibberellin
(d) Ethylene
Answer:
(c) Gibberellin
Question 70.
Which one of the following pairs, is not correctly matched?
(a) Gibberellic acid-Leaf fall
(b) Cytokinin-Cell division
(c) IAA-Cell wall elongation
(d) Abscisic acid-Stomatal closure.
Answer:
(a) Gibberellic acid-Leaf fall
Very Short Answer Type Questions : 1 Mark
Question 1.
Who coined the term phytohormones?
Answer:
Thimann in 1948.
Question 2.
Name the naturally occurring Auxin in plants.
Answer:
Indole Acetic Acid (IAA).
Question 3.
Name one synthetic Auxin used to in the production of seedless fruits.
Answer.
NAA (Naphthalene Acetic Acid).
Question 4.
Name one Auxin that can induce root formation in plant tissue cultures.
Answer:
IAA.
Question 5.
Name a synthetic Auxin that is used as a Weedicide.
Answer:
2, 4, D (2, 4, Dichlorophenoxy Acetic Acid).
Question 6.
Name of hormone that induces bolting in plants.
Answer:
Gibberellin.
Question 7.
Name the meristems responsible for primary growth in plants.
Answer:
Primary meristem/root tip and short tip.
Question 8.
Define growth.
Answer:
It is a permanent and irreversible increase in size or volume accompanied by increase in dry weight/biomass of an organism.
Question 9.
Why seeds are soaked in Gibberellic acid solution before sowing?
Answer:
Gibberellic acid breaks seed dormancy and promotes germination.
Question 10.
Which hormone is linked with phototropic and geotropic movement in plant?
Answer:
Auxin regulates the phototropic and geotropic movement.
Question 11.
Avena Coleoptile test is for
Answer:
Ethylene.
Question 12.
Seed germintion is brought about by
Answer:
Gibberellin.
Question 13.
The following hormone is artifical Auxin
Answer:
NAA.
Question 14.
The following hormone is antiauxin
Answer:
Cytokinin.
Question 15.
Premature leaf fall is brought about by
Answer:
GA,
Question 16.
Cell division is promoted by
Answer:
kinetin.
Question 17.
Which is the natural Auxin?
Answer:
IAA.
Question 18.
Seed germination is induced by which hormone?
Answer:
Auxin.
Question 19.
Which hormone delay leaf senescence?
Answer:
Cytokinin.
Question 20.
Which hormone helps to produce seedless fruits?
Answer:
Synthetic Auxin and synthetic Gibberellin.
Question 21.
Give the full form of IAA?
Answer:
Indole Acetic Acid.
Question 22.
What is synthetic hormone?
Answer:
Artificial hormones are synthesised in the industry and these are artificial Auxin, Gibberellin and Cytokinin. This is called synthetic hormone.
Question 23.
Which hormone helps in optical dormancy in Plant?
Answer:
Auxin.
Question 24.
What do you mean by natural auxin?
Answer:
The hormones that are synthesised naturally are called natural auxin.
Question 25.
Name the precursor of IAA synthesis?
Answer:
Tryptophan.
Question 26.
What is Gibberllin?
Answer:
Non-nitrogenous organic acids having terpenoid group functioning as growth promoting substance are Gibberellins.
Question 27.
What is Auxin?
Answer:
The nitrogenous acidic phytohormones which are synthesised at the tip of the root, coleoptile, shoot, apex etc are called Auxins.
Question 28.
What is Cytokinin?
Answer:
A group of nitrogen containing basic organic compound having a purine group and functioning as growth promoting substances are called Cytokinin.
Question 29.
Name a natural Auxin.
Answer:
Indole Acetic Acid.
Question 30.
Name the phytohormone that helps in seed germination.
Answer:
Gibberellin.
Question 31.
Which hormone is antiauxin?
Answer:
Cytokinin.
Question 32.
Name the hormone that can be used to overcome genetic dwarfism in plants.
Answer:
Gibberellin.
Question 33.
What are growth inhibitors?
Answer:
The hormones which hinder or suppress the growth of plants are called growth inhibitors.
Question 34.
Which phytohormone reduces the rate of transpiration?
Answer:
ABA (Abscisic Acid)
Question 35.
Name the hormone which induces ripening of fruits.
Answer:
Ethylene.
Question 36.
Name the commercially available Ethylene used in ripening of fruits.
Answer:
Ethephon or Ethereal.
Question 37.
What are growth promoters?
Answer:
The phytohormones which promote growth of plants are called growth promoters.
Question 38.
Name the gaseous plant hormone.
Answer:
Ethylene.
Question 39.
Name the hormone that break dormancy in seeds.
Answer:
Gibberellins or Cytokinins
Question 40.
Name the hormone that helps in elongation of internodes in plants.
Answer:
Gibberellins.
Question 41.
Expand the abbreviation-NAA
Answer:
Naphthalene Acetic Acid.
Question 42.
Auxin is
Answer:
Phytohormones.
Question 43.
Auxin is secreted from
Answer:
Meristematic tissue.
Question 44
Give an example of non-nitrogenous plant hormone.
Answer:
Gibberellin is an example of non-nitrogenous plant hormone.
Question 45.
Mention the chemical nature of Auxin and Thyroxine.
Answer:
The chemical nature of Auxin is nitrogenous. The chemical nature of Thyroxine is nitrogenous including iodine molecule.