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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:
- Growth: It is an irreversible and permanent process, accomplished by an increase in the size of an organ or organ parts or even of an individual cell.
- Differentiation: It is a process in which the. cells derived from the apical meristem and the cambium undergo structural changes in the cell wall and the protoplasm, becoming mature to perform specific functions.
- Development: It refers to the various changes occurring in an organism during its life cycle from the germination of seeds to senescence.
- De-differentiation: It is the process in which permanent plant cells regain the power to divide under certain conditions.
- Re-differentiation: It is the process in which differentiated cells become mature again and lose their capacity to divide.
- Determinate growth: It refers to limited growth. For example, animals and plant leaves stop growing after having reached maturity.
- Meristem: In plants, growth is restricted to specialised regions where active cell divisions take place. Such a region is called meristem.
- Growth rate: It can be defined as the increased growth in plants per unit time.
Question 2.
Why is no any one parameter good enough to demonstrate growth throughout the life of a flowering plant?
Answer:
In plants, growth is said to have taken place when the amount of protoplasm increases. Measuring the growth of protoplasm involves many parameters such as weight of fresh tissue sample, weight of dry tissue sample, differences in length, area, volume and cell number measured during the growth period. Measuring the growth of plants using only one parameter does not provide enough information and hence, is insufficient for demonstrating growth.
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 characterised 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.
(c) Sigmoid growth curve:
The growth of living organisms in their natural environment is characterised 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
(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 discovery, physiological functions and agricultural/ horticultural applications of any one of them.
Answer:
Plant growth regulators are the chemical molecules secreted by plants affecting the physiological attributes of a plant. There are five main plant growth regulators.
They are:
- Auxins
- Gibberellic acid
- Cytokinins
- Ethylene
- Abscisic acid
Discovery: During mid-1960s, inhibitor – B, abscission II and dormant were discovered by three independent researches. These were later on found to be chemically similar and were thereafter called Abscisic acid (ABA).
Physiological Functions:
- It acts as an inhibitor to plant metabolism.
- It stimulates stomatal closure during water stress.
- It induces seed dormancy
- It induces abscission of leaves, fruits and flowers.
Horticultural application:
It induces seed dormancy in stored seeds.
Question 5.
What do you understand by photoperiodism and vernalisation? Describe their significance.
Answer:
Photoperiodism refers to the response of plants with respect to the duration of light. On the basis of its response to the duration of light, a plant is classified as a short-day plant, a long-day plant or a day-neutral plant. Photoperiodism helps in studying the response of flowering in various crop plants with respect to the duration of exposure to light.
Vernalisation is the cold-induced flowering in plants. In some plants, exposure to low temperature is necessary for flowering to be induced. The winter varieties of rye and wheat are planted in autumn. They remain in the seeding stage during winters and flower during summers. However, when these varieties are sown in spring, they fail to flower.
Question 6.
Why is abscisic acid also known as stress hormone?
Answer:
Abscisic acid is called stress hormone as it induces various responses in plants against stress conditions. It increases the tolerance of plants towards various stresses. It induces the closure of stomata during water stress. It promotes seed dormancy and ensures seed germination during favourable conditions. It helps seeds withstand desiccation. It also helps in inducing dormancy in plants at the end of the growing season and promotes abscission of leaves, fruits and flowers.
Question 7.
Both growth and differentiation in higher plants are open. Comment.
Answer:
Growth and development in higher plants is referred to as being open because various meristems, having the capacity for continuously dividing and producing new cells, are present at different locations in these plant bodies.
Question 8.
‘Both a short day plant and a long day plant can flower simultaneously In a given place’. Explain.
Answer:
The flowering response in short-day plants and long-day plants is dependent on the duration for which these plants are exposed to light. The short-day plant and long-day plant can flower at the same place, provided they have been given an adequate photoperiod.
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 photoperiodlc cycle? Why?
Answer:
defoliated plant will not respond to the photoperiodic cycle.
It is hypothesised that the hormonal substance responsible for flowering is formed in the leaves, subsequently migrating to the shoot apices and modifying them into flowering apices. Therefore, in the absence of leaves, light perception would not occur i.e., the plant would not lespond to light.
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 cytoklnin 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 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 sigmoid growth curve.
Question 2.
Name the apparatus used In determining growth in the plant? (Oct. 85)
Answer:
Auxanometer
Question 3.
What does log phase of Sigmoid Growth curve represent? (Apr. 96)
Answer:
The phase of cell elongation
Question 4.
Define growth curve. (M.Q.P.)
Answer:
Growth curve is a plot of growth (height, weight or volume) increase plotted against time.
Question 5.
Describe a growth Inhibitor with 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.
What is the result of addition of gibberellins to plants? (Oct. 91)
Answer:
Bolting
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.
Define photoperiodism. (Apr. 97)
Answer:
The response of a plant to varying photoperiods of light is called photoperiodism.
Question 11.
What Is meant by parthenocarpy? (Oct. 97, Apr. 99)
Answer:
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:
In 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 an indeterminate growth?
Answer:
In 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 an apical dominance?
Answer:
The influence of 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.
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.
Question 3.
Define the term Growth. Mention the phases of growth. (Oct. 1988, 2000, 2003, July 2006, March 2011)
Answer:
Growth is a permanent irreversible change brought about by an increase in size, weight or volume. The phases of growth are
- Phase of cell division or formation
- Phase of cell elongation or enlargement
- Phase of cell maturation or differentiation.
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 dichlorophenoxy acetic acid) used as weedicide.
NAA (Napthalene acetic acid) – Initiates floweripg 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 Gibberelllns. (July 07, 09)
Answer:
Practical applications of Gibberellins
- Bolting and flowering brings about stem elongation called bolting and 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 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 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, formation of arenchyma 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 ex-amples.
Answer:
The substances similar to auxins 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.
Abscissic acid is known as dormin. (July 2010)
Answer:
Abscissic acid causes the suppression of axillary birds which fail to grow creating a condition of dormancy, hence called dormin.
1st PUC Biology Plant Growth and Development Five Marks Questions
Question 1.
Define growth and describe the three phases of growth. (Oct. 83, 85)
Answer:
Growth is a permanent irreversible change brought about by increase in height, weight or volume. The three phases of growth are;
(a) Phase of cell division or cell formation:
This region is located at the tip of shoot and root. It is represented by the apical meristem capable of rapid cell division. The cells are undifferentiated, with a thin cell wall made of cellulose, with an active protoplasm and prominent nucleus. This region is mainly concerned with cell division.
(b) Phase of cell elongation or cell enlargement: This region lies next to the cell formation zone. The cells enlarge because of their elastic cell walls. Growth takes place during this stage either by apposition or intusucception. Cells are turgid.
(c) Phase of cell differentiation or cell maturation: This represents the last region and differentiation based on functions is seen here. Secondary walls are laid down where some have additional deposits of lignin, Suberin and others lose their protoplast and become dead.
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. 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 inflexion 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. 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 % this process.
(d) Gibberellins break dormancy and help in promoting seed germination by sythesising a-amylase.
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 which they are grouped as Long day, short day and day-neutral plants. This phenomenon was studied by Garner and Allard quality is 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.
Discuss the practical applications of auxins in Agriculture and Horticulture. (Oct. 96) OR What are auxins? Explain briefly uses of Auxins. (Oct. 99)
Answer:
Auxins are a group of plant growth substances, acidic in nature and bring about over-all growth.
- Apical dominance: As long as the apical bud is present growth of lateral buds is pre-vented which is used in the long term storage of potato tubers.
- Rooting: In low concentrations, auxins stimulate root formation which is used to propagate cuttings. When dipped in a dilute solution of auxins the root formation is initiated.
- Flower initiation: Low Concentration of 2, 4-D and NAA are used to initiate flowering in a pineapple so that harvesting becomes easy.
- Abscission: Application of auxins increase the concentration and thereby delays the development of abscission which prevents premature leaf and fruitful. This is used in orchards and prevention of defoliation in cabbages and cauliflower.
- Parthenocarpy: This is the process of obtaining fruits without fertilization and gives rise to seedless varieties which is successfully used in citrus, dates.
- Sex expression: Use of auxins on cucurbit plants increases the production of female flower.
- Weedicide / Herbicide: 2-4-D is widely used as a herbicide on broad-leaved forms because of its non-toxic nature. Widely used in crop plant cultivation or lawns.
- Tissue culture (organogenesis): In tissue culture where micropropagation is carried out the auxins are used to bring about organogenesis.
Question 6.
Discuss the role of auxins in plant growth.
OR
Describe any four physiological effects of auxins. (Oct. 89, 2001)
Answer:
(1) Cell division and Differentiation: Auxins promote cell division and their subsequent differentiation into tissues. They are used in cultures to bring about organogenesis.
(2) Apical dominance: Auxins are more concentrated in the terminal buds rather than lateral buds. Therefore the presence of the terminal buds inhibits the growth of lateral buds which is also true when auxins are applied to the cut surface of the stem. This is used in preventing the sprouting of potato buds (axillary buds).
(3) Root Initiation: Low concentrations of auxins promote rooting which can propagate more plants vegetatively.
(4) Abscission formation: Development of abscission is due to a decrease in auxin concentration resulting in fruit fall and defoliation. In young leaves and fruits, the concentration is high. Hence the external application of auxins helps to prevent premature fruit drop of apple, pear and defoliation of cabbage.
(5) Parthenocarpy: A normal fruit develops after fertilization, during which the auxin concentration increases. Application of auxins stimulate fruit formation without fertilization and is called parthenocarpy.
(6) Herbicide: Synthetic auxins like 2, 4 – D and 2, 4, 5-T are toxic to broad-leaved plants and because of this used as selective herbicides in crop plants, lawn grass etc.