1st PUC Biology Question Bank Chapter 15 Plant Growth and Development

   

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Karnataka 1st PUC Biology Question Bank Chapter 15 Plant Growth and Development

1st PUC Biology Plant Growth and Development NCERT Text Book Questions and Answers

Question 1.
Define growth, differentiation, development, dedifferentiation, differentiation, determinate growth, meristem, and growth rate.
Answer:

  1. Growth: Growth is a permanent and irreversible increase in the size of living structure which is accompanied by an increase in dry weight and the amount of protoplasm.
  2. Differentiation: The cells are derived from root apical and shoot apical meristems and cambium differentiate and mature to perform specific functions. This act leading to maturation is called as differentiation.
  3. Development: Development includes all changes in an organism which occur during the life-cycle from seed germination to growth, maturation, and senescence. Development is a qualitative change referring to the changes in the nature of growth made by an organism.
  4. Dedifferentiation: The living differentiated cells lose their capacity of division. These cells may regain their capacity to divide under certain conditions. This phenomenon is called as dedifferentiation.
  5. Redifferentiation: The products of dedifferentiated cells which lose the capability to divide but mature to perform specific functions are called redifferentiated cells. This phenomenon is called as redifferentiation.
  6. Determinate growth: When growth occurs only for some time it is called as determinate growth.
  7. Meristems: Meristems are cells that divide continuously to produce new cells.
  8. Growth rate: The expression of increased growth per unit time is called growth rate.

Question 2.
Why is no one parameter good enough to demonstrate growth throughout the life of a flowering plant?
Answer:
Growth, at a cellular level, is a consequence of the increase in the amount of protoplasm, which is difficult to measure directly. As a result, growth is manifested in different forms. It may be manifested as an increase in weight or volume, length or cell number, or a combination of these so no single parameter can be used.

Question 3.
Describe briefly:
(a) Arithmetic growth
(b) Geometric growth
(c) Sigmoid growth curve
(d) Absolute and relative growth rates
Answer:
(a) Arithmetic growth:
In arithmetic growth, one of the daughter cells continues to divide, while the other differentiates into maturity. The elongation of roots at a constant rate is an example of arithmetic growth.

(b) Geometric growth:
Geometric growth is characterized by a slow growth in the initial stages and a rapid growth during the later stages. The daughter cells derived from mitosis retain the ability to divide but slow down because of limited nutrient supply.

KSEEB Solutions

(c) Sigmoid growth curve:
The growth of living organisms in their natural environment is characterized by an S-shaped curve called sigmoid growth curve. This curve is divided into three phases, lag phase, log or exponential phase of rapid growth and stationary phase
1st PUC Biology Question Bank Chapter 15 Plant Growth and Development 1

(d) Absolute and relative growth rates:
Absolute growth rate refers to the measurement and comparison of total growth per unit time. Relative growth rate refers to the growth of a particular system per unit time, expressed on a common basis.

Question 4.
List five main groups of natural plant growth regulators. Write a note on the discovery, physiological functions and agricultural/ horticultural applications of any one of them.
Answer:
Plant growth regulators (PGRs) are variously described as plant growth substances, plant hormones, or phytohormones in literature. The PGRs can be broadly divided into two groups based on their functions in a living plant body. One main group of PGRs are involved in growth-promoting activities, such as

  1. Cell division
  2. Cell enlargement
  3. Pattern formation
  4. Tropic growth
  5. Flowering
  6. Fruiting and
  7. Seed formation

These are also called plant growth promoters e.g., auxins, gibberellins, and cytokinins. The discovery of plant growth regulators: Interestingly, the discovery of each of the five major groups of PFRs have been accidental. All this started with the observation of Charles Darwin and his son Francis Darwin when they observed that the coleoptiles of canary grass responded to unilateral illumination by growing towards the light source (phototropism). After a series of experiments, it was concluded that the tip of the coleoptile was the site of transmittable influence that caused the .bending of the entire coleoptile. The auxin was discovered by F.W. Went from coleoptile tips of an oat seedling.

The ‘balance’, (foolish seedling) disease of rice seedlings was caused by a fungal pathogen Gibberalla Fujikuroi. E.Kurosawa reported the appearance of symptoms of the disease in uninfected rice seedlings when they were treated with sterile filtrates of the fungus. The active substances were later identified as gibberellic acid.

F. Skoog and his co-workers observed that from the intermodal segments of tobacco stems the callus proliferated only if, in addition to auxins nutrients the medium was supplemented with one of the following: extracts of Vascular tissues, yeast extract, coconut milk, or DNA. Skoog and Miller later identified and crystallized the cytokinesis promoting active substances that they termed kinetin.

During the mid-1960s, three independent researchers reported the purification and chemical characterization of three different kinds of inhibitors; inhibitor-B, abscission II, and dormant. Later all these were proved to be chemically identical. It was named abscisic acid (ABA).

Physiological functions and agricultural/horticultural applications: Auxins, like IAA and indole butyric acid (IBA) have been isolated from plants. NAA (naphthalene acetic acid) and 2,4 -D (2,4 -dichloro phenoxy- acetic) are synthetic auxins. All these auxins have been used extensively, in agricultural and horticultural practices.

They help to initiate rooting in stem cuttings, an application widely used for plant propagation. Auxins promote flowering e.g. in pineapples. They help to prevent fruit and leaf drop at early stages but promote the abscission older of mature leaves and fits.

In most higher plants, the growing apical bud inhibits the growth of the lateral (axillary) buds, a phenomenon called apical dominance. Removal of shoot tips (decapitation) usually results in the growth of lateral buds. It is widely applied in tea plantations, hedge making. Auxins also induce parthenocarpy e.g. in tomatoes. They are widely used as herbicides. 2, 4 -D, widely used to kill dicotyledonous weeds, does not affect mature monocotyledonous plants. It is used to prepare lawns by gardeners. Auxin also controls xylem differentiation and helps cell-division.

Gibberellins: Gibberellins are another kind of promoter PGR. Sug-arcane stores carbohydrates as sugar in their stems. Spraying sugarcane crop with gibberellins increases the length of the stem. Thus increasing the yield by as much as 20 tonnes per acre.
Cytokinins: Natural cytokinins helps to produce new leaves, chloro- plants in leaves, lateral shoot growth, and adventitious shoot formation. Cytokinins help overcome apical dominance. They promote nutrient mobilization which helps in the delay of leaf senescence.

Question 5.
What do you understand by photoperiodism and vernalisation? Describe their significance.
Answer:
Photoperiodism: Flowering in certain plants depends not only on a combination of light and dark exposures but also on their relative durations. This response of plants to periods of day/night is termed photoperiodism. Some hormonal substances (e.g. florigen) migrate from leaves to shoot apices for inducing flowering only when the plants are exposed to the necessary inductive photoperiod.

Vernalization: It is the process of enabling low temperature to some temperate plants artificially so as to reduce the duration of vegetative phase and initiate the onset of reproductive phase or flowering verialisation has been successfully used in many winter annuals biennial plants, e.g. winter wheat winter barley, winter lye, winter rat, cabbage, pea, but, etc.

Question 6.
Why is abscisic acid also known as stress hormone?
Answer:
Abscisic acid (ABA) was discovered for its role in regulating abscission and dormancy. But, like other PGRs, it also has wide-ranging effects on plant growth and development. It acts as a general plant growth inhibitor and an inhibitor of plant metabolism. ABA inhibits seed germination. ABA stimulates the closure of stomata in the epidermis and increases the tolerance of plants to various kinds of stresses. Therefore, it is also called the stress hormone. ABA plays an important role in seed development, maturation and dormancy. By inducing dormancy, ABA helps seeds to withstand desiccation and other factors unfavorable for growth. In most situations, ABA acts as an antagonist to GAs.

Question 7.
Both growth and differentiation in higher plants are open. Comment.
Answer:
In higher plants, new cells are always being added to the plant body by the activity of the meristem. This ability of the plants is due to the presence of meristems at certain locations in their body. Meristems have the capacity to divide and self-perpetuate. The cells formed by these meristems later differentiate into different types of tissues and organs.

Question 8.
‘Both a short day plant and a long day plant can flower simultaneously In a given place’. Explain.
Answer:
Some plants require exposure to light for a period exceeding a well-defined critical duration, while others must be exposed to light for a period less than this critical duration before the flowering is initiated in them. The former group of plants is called short-day plants while the later ones are termed long-day plants.

In short-day plants, it is the length of the uninterrupted night that is more important than the day length. If a long night is broken by a brief flash of light into two short nights, flowering will not occur, If however, light (red light) is followed by a flash of far-red light, flowering occurs. If a series of red, far-red lights are given to a plant in quick successions during the night, it is the last treatment that will determine the type of response, i.e., Red= no flowering, Far red= flowering.

Those plants which produce flower only when the day length is more than a critical photoperiod are called long-day plants. They can produce flowers even under continuous illuminations, e.g., Spinacia, Hyoscyamus niger.

Question 9.
Which one of the plant growth regulators would you use If you are asked to:

(a) induce rooting in a twig
Answer:
Auxins

(b) quickly ripen a fruit
Answer:
Ethylene

(c) delay leaf senescence
Answer:
Cytokinins

(d) induce growth In axillary buds
Answer:
Cytokinins

(e) ‘bolt’ a rosette plant
Answer:
Gibberellic acid

(f) Induce Immediate stomatal closure in leaves.
Answer:
Abscisic acid

Question 10.
Would a defoliated plant respond to the photoperiodic cycle? Why?
Answer:
No, because the site of perception of light/dark durations is leaves which is absent in defoliated plant, hormone florigen will not migrate to shoot apices to induce flowering.

KSEEB Solutions

Question 11.
What would be expected to happen If:

(a) GA3 is applied to rice seedlings
Answer:
If GA3is applied to rice seedlings, then the rice seedlings will exhibit internode elongation and increase in height.

(b) Dividing cells stop differentiating
Answer:
If dividing cells stop differentiating, then
the plant organs such as leaves and stem will not be formed. The mass of undifferentiated cell is called callus.

(c) A rotten fruit gets mixed with unripe fruits
Answer:
If a rotten fruit gets mixed with unripe fruits, then the ethylene produced from the rotten fruits will hasten the ripening of the unripe fruits.

(d) you forget to add cytokinin to the culture medium.
Answer:
If you forget to add cytokinin to the culture medium, then cell division, growth and differentiation will not be observed.

1st PUC Biology Plant Growth and Development Additional Questions and Answers

1st PUC Biology Plant Growth and Development One Mark Questions

Question 1.
What is meant by a sigmoid growth curve? (Apr. 84, 87, Oct. 91, 2001)
Answer:
The S-shaped growth curved obtained when plotting height, weight or volume of the plant at successive intervals against time is termed the sigmoid growth curve.

Question 2.
Name the final acceptor of an electron in ETC.
Answer:
Zeatin obtained from com-kernels and coconut milk.

Question 3.
What does log phase of the Sigmoid Growth curve represent? (Apr. 96)
Answer:
The phase of cell elongation

Question 4.
Define growth curve. (M.Q.P.)
Answer:
A growth curve is a plot of growth (height, weight, or volume) increase plotted against time.

Question 5.
Describe a growth Inhibitor with an example. (Apr. 98)
Answer:
A growth inhibitor is one which inhibits or has negative effects on growth. Abscisic acid is a growth inhibitor.

Question 6.
Name the fungus from which Gibberellin was discovered. (Oct. 86)
Answer:
Gibberella fujikuroi

Question 7.
Why is a beetroot plant called a long day plant?
Answer:
The beetroot plant is called a long day plant because it requires a light period longer than the critical photoperiod for flowering.

Question 8.
Which hormone induces parthenocarpy?
Answer:
Auxins & gibberellins (Oct. 94)

Question 9.
Name the hormone present in the liquid endosperm of coconut. (Apr. 95)
Answer:
Cytokinin

Question 10.
Name the plant in which Darwin first observed phototropic curvature.
Answer:
Darwin firstly observed phototropic curvature in canary grass.

Question 11.
What Is meant by parthenocarpy? (Oct. 97, Apr. 99)
Answer:
The formation of fruits without fertilization is called parthenocarpy.

Question 12.
Which hormone is abbreviated as ABA?
Answer:
Abscisic Acid (Oct. 97)

Question 13.
Name the most naturally occurring Auxin. (M.Q.P., Oct. 98, 2003)
Answer:
Indole Acetic Acid.

Question 14.
‘Bakana disease’ is associated with the discovery of which hormone? (Apr. 01)
Answer:
Gibberellins

Question 15.
What is vernalization? (Apr. 2002)
Answer:
The response of a plant to low temperature resulting in flowering is called vernalization.

Question 16.
What is determinate growth?
Answer:
This growth occurs only up to a particular age. Certain plant organs like leaves grow to a certain size, then they become old and die.

Question 17.
What is indeterminate growth?
Answer:
This growth continues to take place throughout the life span. The stem, root show indeterminate growth.

Question 18.
What are growth regulators?
Answer:
The substances which they regulate growth are called growth regulators.

Question 19.
What are growth promoters?
Answer:
Some plant hormones promote growth. So they are called growth promoters.

Question 20.
What is apical dominance?
Answer:
The influence of the apical bud in suppressing the growth of lateral buds is called apical dominance.

Question 21.
What is bolting?
Answer:
The linear growth of rosette plants accompanied by flowering is called bolting.

Question 22.
Which hormone induces apical dominance.
Answer:
Auxin or IAA.

Question 23.
Expand IBA. (Apr. 2006)
Answer:
Indole Butyric Acid.

Question 24.
Give reasons for the following:
(a) Removal of Apical buds in some plants makes them to grow bushy. (Apr. 2006)
Answer:
It is principle of apical dominance where in lateral buds start growing after removal of apical buds resulting in bushy growth of plants.

KSEEB Solutions

Question 25.
Fruit flies swarm around ripe banana. Why?
Answer:
Flies are attracted by the presence of ethylene. (July 2006)

Question 26.
Give reasons for the followings: (July 2006)
(a) 2,4-D is effective as a weed killer in cereal crop fields.
(b) Fruits of some plants are naturally seedless.
Answer:
(a) 2, 4-D is effective as a weed killer in cereal crop fields because of its selective action towards dicots only which are destroyed
(b) When fruits develop without fertilization as in banana the seeds become abortive and the fruit naturally seedless.

Question 27.
Meristematic cells show high rate of respiration. (July 2007)
Answer:
These cells are metabolically active hence show high rate of respiration.

Question 28.
Give reason: (March 2008)
All parthenocarps are seedless fruits.
Answer:
Parthenocarpic fruits develop without fertilization, hence the seeds are abortive and become seedless.

Question 29.
Give reason:
Axillary buds of many plants remain normally suppressed (June 2009)
Answer:
Axillary buds of many plants are normally suppressed because of apical dominance of the terminal bud.

Question 30.
What is Richmond-Lang effect? (March 2011)
Answer:
The Richmond-Lang effect is the delay in the process of ageing by application of cytokinins.

1st PUC Biology Plant Growth and Development Two Marks Questions

Question 1.
What is sigmoid curve? Explain. (Apr. 94, Oct. 97)
Answer:
The S shaped growth curve obtained when plotting height, weight or volume of the plant at successive intervals against time is termed sigmoid growth curve. The graph obtained shows three important phases, the initial period of slow growth called lag phase, followed by a period of rapid growth called log phase and a decreasing state after which growth becomes steady. The total time during which the plant shows an increase is called grand period of growth.

Question 2.
Sketch the growth curve and mention the phases. (M.Q.P., July 06, 07, 2011 April 07)
Answer:
The S shaped growth curve obtained when plotting height, weight or volume of the plant at successive intervals against time is termed sigmoid growth curve. The graph obtained shows three important phases, the initial period of slow growth called lag phase, followed by a period of rapid growth called log phase and a decreasing state after which growth becomes steady. The total time during which the plant shows an increase is called grand period of growth.
The phases of growth are lag phase, log phase and steady-state.
1st PUC Biology Question Bank Chapter 15 Plant Growth and Development 2

Question 3.
Why is the term ‘ long day plant’ a misnomer?
Answer:
Flowering in the long-day plant is determined by the period of a short night. Thus the appropriate term for these plants is – ‘short night plants’.

Question 4.
Define Photoperiodism. Classify plants based on this phenomenon. (Apr. 1991)
Answer:
The response of a plant varying photo-periods of light is called photoperiodism.
Plants are grouped into 3 types;

  • Long day plants eg- spinach, beetroot
  • Short day plants eg- tobacco, soybean
  • Day-neutral plants eg- tomato, chilli

Question 5.
Name two synthetic auxins. Give one practical application of each. (Apr. 96)
Answer:
Synthetic auxins are;
2,4 – D (2, 4 dichloro phenoxy acetic acid) used as weedicide.
NAA (Naphthalene acetic acid) – Initiates flowering in pineapple.

Question 6.
Give four practical applications of Gibberellins.
(Oct. 95, 02, Apr. 97, M.Q.P., March 2011)
OR
Mention any four physiological applications of Gibberellins. (July 07, 09)
Answer:
Practical applications of Gibberellins

  • Bolting and flowering bring about stem elongation called bolting and the formation of flowers in Cabbage and cauliflower.
  • Breaking dormancy: They break dormancy and promote germination.
  • Parthenocarpy: Induce the formation of parthenocarpic fruits and more potent than auxins.
  • Synthesis of enzyme amylase: They induce synthesis of a amylase in the endosperms of germinating grains.

Question 7.
Mention tie applications of synthetic auxins. (M.Q.P.)
Answer:
Synthetic auxins are widely used in

  • Inducing rooting
  • Parthenocarpy
  • Weed Control
  • Inhibition of Abscission.

Question 8.
Mention any four practical applications of Auxins. (Oct. 98, 2004)
Answer:

  • Apical dominance – used for long-term storage of potato tubers.
  • Parthenocarpy – used in the production of seed¬less fruits
  • Abscission – to prevent premature fruitful and defoliation of cabbage.
  • Weedicide – to destroy dicots in crop cultivation and Lawn grass patches.

Question 9.
Mention any four uses of phytohormones in Agriculture and Horticulture. (Apr. 99)
Answer:
The four uses of phytohormones are to induce flowering, parthenocarpy, weedicide, Development of abscission, and Bolting.

Question 10.
Describe any two applications of gibberellins. (Apr. 2000)
Answer:

  • Bolting:- Stem elongation is brought about by the application of gibberellins which is used in inducing flowering in cabbages and cauliflower. It also converts a mutant dwarf to a tall.
  • Breaking dormancy:- Dormancy periods of seeds are reduced and induces them to germinate.

Question 11.
Mention any 2 applications of ethylene hormone. (Apr. 2001)
Answer:
Fruit ripening, the formation of aerenchyma and latex cells.

Question 12.
Mention two functions of abscisic acid.
(Oct. 2001, March 2009)
Answer:
The functions of abscisic acid are;

  • Abscission – which promotes senescence of leaves.
  • Stomatal closure – by doing so it acts as a stress hormone and helps to cope with drought.

Question 13.
Write any two applications of IBA.
Answer:

  • Fruit setting: IBA is used to improve fruit setting in trees.
  • Root formation: IBA is used to induce rapid root formation in cuttings.

Question 14.
Write any two applications of 2,4 – D.
Answer:

  • Parthenocarpy: 2, 4 – D is used to induce parthenocarpic development of fruits.
  • Eradication of weeds: Unwanted harmful weeds can be killed by spraying 2, 4 – D. The concentration of 2,4 – D which is used is 100 – 150 ppm (parts per million).

Question 15.
What are growth promoters? Give two examples?
Answer:
The hormones which promote growth are called growth promoters.
Example:

  • Auxins
  • Cytokinins.

Question 16.
What are growth inhibitors? Give two examples.
Answer:
The hormones which inhibit growth are called growth inhibitors.
Example:  ABA, Ethylene.

Question 17.
What are synthetic auxins? Give two examples.
Answer:
The substances similar to auxins that have been synthesized in the laboratory are called synthetic auxins. Example: IBA, NAA.

Question 18.
What are growth regulators? List any two applications of gibberellins. (Apr. 2006)
Answer:
Growth regulators are chemical substances which regulate growth i.e. either promote or retard growth. Applications of gibberellins are

  • Bolting: Stem elongation, a property used to induce flowering in cabbages and cauliflower.
  • Breaking dormancy: reduces the dormancy period of seeds and induces them to germinate.

Question 19.
Mention two commercial applications of NAA (Naphthalene Acetic Acid). (July 2008, March 2009)
Answer:
Commercial applications of NAA:

  • Induce flowering in pineapple.
  • Root setting hormone.
  • Natural fruit setting in some species.

Question 20.
Expand the abbreviation 2,4,5-T and write its importance. (July 2010)
Answer:
2,4,5-Trichlorophenoxy acetic acid. It used as a selective weedicide.

Question 21.
Abscisic acid is known as dormin. (July 2010)
Answer:
Abscisic acid causes the suppression of axillary birds which fail to grow to create a condition of dormancy, hence called dormin.

1st PUC Biology Plant Growth and Development Five Marks Questions

Question 1.
Describe three different actions of ethylene in plants.
Answer:
horizontal growth of seedlings, breaking seed and bud dormancy, initiates germination in peanut seeds, sprouting of potato tubers. Ethylene promotes rapid internode/petiole elongation in deepwater rice plants.

It is highly effective in inducing fruit ripening when it is produced in large amounts. Ethylene increases the permeability of cells because of which the fruit is softened and the entry of oxygen into fruit is accelerated.

Question 2.
Define growth. Describe an experiment to measure the rate of growth by Lever (Arc)
Auxanometer(Apr. 93, Oct. 97)
Answer:
Define growth: growth is a permanent irreversible change brought about by an increase in height, weight, or volume. A growth curve is a plot of the increase in the height, weight or volume of a plant or its parts against time. In the initial stages, growth is slow and is represented by the lag phase followed by a sudden phase of rapid growth called log phase or exponential growth.

The total time during which growth increase is called the grand period of growth a term used by Julius Sachs. This is followed by a decreasing growth rate where a decline in growth is seen and the point at which it occurs is called the inflection point. After this, the growth stops and is called the steady-state or the stationary phase. This portion depends upon the type of plant. The shape of the graph is ‘S’ shaped, so-called the sigmoid growth curve.

Question 3.
Give four uses of plant hormones. (Apr. 83)
Answer:
Uses of plant hormones:
(a) Auxins show apical dominance: As long as the apical bud is present it prevents the growth of lateral buds. This is used in the long-term storage of potato tubers.

(b) Auxins control abscission: This is a process by which leaves and fruits drop from a tree by the formation of the abscission. An increase in auxin concentration prevents the formation of this layer and is used to prevent defoliation of leaves in cabbage and cauliflower.

(c) Gibberellins show Bolting: This results in an elongation of stem and used to induce flowering in Cabbage and Cauliflower. A genetically dwarf plant is converted to a tall by % of this process.

(d) Gibberellins break dormancy and help in promoting seed germination by synthesizing a-amylase.

KSEEB Solutions

Question 4.
Describe four factors that affect growth. (Oct. 92)
Answer:
Factors that affect growth are Light, temperature, water supply, oxygen.
Light: Its effects can be grouped under intensity, duration, and quality. Intensity refers to the brightness and based on this requirement plants are grouped as Heliophytes and sciophytes. Heliophytes require bright sunlight, if not available they tend to show etiolated conditions and internodes are considerably long.

Duration is the response of plants to varying periods in which they are grouped as Long day, short day and day-neutral plants. This phenomenon was studied by Garner and Allard quality is the wavelength and in general, plants grow best in visible light.

Temperature: This directly affects the action of enzymes which function best within an optimum range. Temperature influences plant growth in the case of flowering and the process is called vernalization. For some plants mainly biennials flowering is governed by photoperiod and temperature. It is the low temperature during the first year that influences the response.

Water: It is required for all the fundamental processes, of the protoplasm and is essential for cell enlargement as it increases turgidity.

Oxygen: The Vital activities are dependent on the release of metabolic energy by respiration. The energy held in the chemical bond of fuel molecules can be released which stimulated growth.

Question 5.
What is the sigmoid growth curve? Write the names of the three phases in it.
Answer:
S-growth curve: The rate of growth whether measured as length area, volume or weight is not uniform. Under ideal conditions when the rate of growth is plotted against time, an S-shaped curve called the sigmoid curve.

  • Lag phase: Growth is slow in the initial stage.
  • Exponential period of growth: It is the second phase of maximum growth. Here, both the progeny cells follow mitotic cell division retain the ability to divide.
  • Stationary phase: When the nutrients become limiting, growth slows down.

Question 6.
Discuss the role of gibberellins in plant growth and development.
Answer:
The role of gibberellins in plant growth and development are as follows:

  • The gibberellins induce elongation of the internodes. The elongation of stem due to rapid cell division and cell elongation.
  • In many plants leaves become broader and elongated when treated with gibberellic acid. This leads to an increase in the photosynthetic area which finally increases the height of the plant.
  • They cause fruits like apples to elongate and improve their shape.
  • They also delay senescence.
  • GA3 increases the yield of malt from barley grains.
  • Spraying of sugarcane crop with gibberellins increases the length of stem and yield of sugarcane to as much as 20 tonnes/ acre.
  • They also promote bolting (internode elongation just prior to flowering) in beet, cabbages, and many plants with rosette habit.
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