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

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

1st PUC Biology Plant Growth and Development One Marks Questions and Answers

Question 1.
Expand IBA.
Answer:
Indole Butyric Acid.

Question 2.
Expand NAA.
Answer:
Naphthalene Acetic Acid.

Question 3.
Name the hormone which brings about inter nodal elongation?
Answer:
Gibberellin.

Question 4.
Which hormone is responsible for premature withering of fruits?
Answer:
Abscissic acid.

Question 5.
Name the fruits ripening hormone.
Answer:
Ethylene.

Question 6.
Define vernalisation.
Answer:
The phenomenon of making the plants to flower by cold treatment followed by correct photoperiod is called vernalisation.

Question 7.
What is bolting?
Answer:
Internode elongation, and early flowering induced by gibberellins is called bolting.

Question 8.
Define growth.
Answer:
Growth can be defined as a permanent irreversible increase in size and volume of a cell, tissue, organ or organism accompanied by an increase in dry weight.

Question 9.
What are the growing regions of the plant body?
Answer:
The meristematic regions or meristems are the growing regions of the plant body.

Question 10.
Mention the phases of growth.
Answer:
The phases of growth are.
(a) Cell division phase
(b) Cell elongation phase
(c) Cell maturation phase or differentiation phase.

Question 11.
Name the auxin which is used as a weedicide.
Answer:
2,4-Dichlorophenoxy acetic acid.

Question 12.
Name the synthetic ethylene releasing compound used as a fruit ripener.
Answer:
Ethephon.

Question 13.
Which is commonly used as a selective weed killer?
Answer:
2, 4 Dichlorophenoxy acetic acid.

Question 14.
Name the hormone responsible for bolting in biennials plants?
Answer:
Gibberellins

Question 15.
Name the hormone responsible for Richmond – lang effect in plants.
Answer:
Cytokinin

1st PUC Biology Plant Growth and Development Two Marks Questions and Answers

Question 1.
Expand apical dominance?
Answer:
When an apical bud is removed in a plant, the lower axillary buds grow rapidly, and the plant becomes profusely branched. If the apical bud is retained, the growth of the lateral bud is suppressed. This phenomenon is called apical dominance. Apical dominance is due to the high concentration of auxins at the apex.

Question 2.
Explain the grand-period of growth.
Answer:
The second phase of growth in the growth curve is called the grand period of growth because in this phase, the growth is rapid due to the enlargement of newly formed young cells. This period of growth is known as log phase or exponential phase.

Question 3.
Explain any two practical/applications of auxins.
Answer:
The practical applications of auxins are:
(a) Auxins induce the rapid cell division, and cell elongation.
(b) Auxins are used in the prevention of premature withering of leaves, flowers and fruits.

Question 4.
Explain any two functions of Gibberellins?
Answer:
The functions of gibberellins are:
(a) Gibberellins are helpful in the elongation of internodes in genetically dwarf plants.
(b) Gibberellins are used to break down the dormancy of seeds and buds.

Question 5.
What are growth regulators? List any two applications of gibberellins.
Answer:
Growth regulators are organic substances produced naturally in minute quantities by highef plants in some particular cells, and are specifically transported to a target organ where they influence physiological functions. They can be either growth promoters or growth inhibitors.

Applications of Gibberellins:
(a) Gibberellins are helpful in the elongation of internodes in genetically dwarf plants.
(b) Gibberellins are used to breakdown the dormancy of seeds, and buds.

Question 6.
Draw a graph showing the typical growth curve and mark the phases of growth in it.
Answer:

Question 7.
Write any two applications of synthetic auxins.
Answer:
(a) Synthetic Auxins like NAA or IBA is used in nurseries to induce adventitious roots by dipping the ends in a dilute solution.
(b) Synthetic 2, 4 – D is a selective weedicide, used to eradicate dicot weeds in monocot plantations.

Question 8.
Mention any two commercial applications of NAA.
Answer:
(a) To produce parthenocarpic fruits like grapes, orange, tomato etc.
(b) To promote flowering of the entire crop at a time, in pineapple, cotton, maize etc.

Question 9.
Mention two physiological functions of abscissic acid.
Answer:
(a) It is a powerful growth inhibitor and inhibits the growth by retarding cell division and cell elongation.
(b) It inhibits seed germination. It induces seed, and bud dormancy.

Question 10.
Why is abscisic acid also known as stress hormone?
Answer:

• It is also called as a stress hormone as it helps the plant to overcome adverse conditions like drought, íkoding. injury etc.
• Synthesised into fruits and leaves.
• First discoverd by Add Scott
• ABA Stimulates the formation of the abscission layer at the stalks of buds, leaves, petals and fruits and caused abscission.
• Can promote seed dormancy, d bud dormancy.
• Stimulates st,rnitiì closure.
• Can decrease RNA and Protein synthesis in leaves.

Question 11.
‘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 12.
Would a defoliated plant respond to photoperiodic cycle? Why?
Answer:
No. as it cannot perceive light, it cannot respond to photoperiodic cycle.

Question 13.
What is vernalization? How does this help in cultivation of winter variety of wheat?
Answer:
Besides correct photoperiod, some plants require low temperature treatment for flowering. This treatment is known as vernalization.

Vernalization prevents precocious reproductive development late in the growing season, and enables the plant to have sufficient time to reach maturity.

Certain food plants like wheat, barley and  have two varieties called,

• Spring variety, and
• Winter variety.

The spring variety is planted in spring, and it completes the lifecycle before the growing season. The winter variety is normally planted in autumn or spring and is harvested by mid-summer.

1st PUC Biology Plant Growth and Development Three Marks Questions and Answers

Question 1.
Describe briefly:
(a) Arithmetic growth.
(b) Geometric growth.
(c) Sigmoid growth curve.
(d) Absolute and relative growth rates.
Answer:
(a) Arithmetic growth refers to the situation where a population increases by a constant number of persons (or other objects) in each period being analysed.

(b) Growth Rate:
The increase in growth per unit time is termed as growth rate. Rate of growth may be arithmetic or geometric. In arithmetic growth, one of the daughter cells formed by mitosis continues to divide, while the other undergoes differentiation and maturation. In Geometrical growth, both the daughter cells formed after mitosis, retain the in ability to divide.

(c)

• Growth can be defined as a permanent and irreversible change in the size, volume or weight of a plant or its parts.
• Plants show two types of growth, namely primary and secondary. Primary growth takes place at the stem or root tips, and it results in the growth in length. Secondary growth takes place due to the activity of cambium, and it results in the growth in thickness.
• In plants the growth is a localised phenomena.

(d) The measurement of total growth per unit time and its comparison is known as absolute growth while the growth of a particular system per unit time is called relative growth rate, it is expressed on a common basis.

Question 2.
What do you understand by photoperiodism and vernalisation? Describe their significance.
Answer:
Photoperiodism :
Plants, in order to flower, require a particular day length or light period called photoperiod and response of the plants to photoperiod in terms of flowering is called photoperiodism. Photoperiodism was first studied by W.W. Garner, and H.A. Allard.

Based on their photoperiodic responses, plants are classified into the following groups:
(1) Long Day Plants: These flower in photoperiod more than critical day length, eg : Wheat, oats etc.
(2) Short Day Plants: These flower in photoperiod less than critical day length. e.g: Tobacco, Chrysanthemums etc.
(3) Day Neutral Plants: These are the plants which are not influenced by the duration of light for their flowering. e.g: Tomato, cucumber, cotton etc.

Vernalisation :
Besides correct photoperiod, some plants require low temperature treatment for flowering. This treatment is known as vernalization.

Vernalization prevents precocious reproductive development late in the growing season, and enables the plant to have sufficient time to reach maturity.

Certain food plants like wheat, barley and rye have two varieties called,
(i) Spring variety, and
(ii) Winter variety.
The spring variety is planted in spring, and it completes the lifecycle before the growing season. The winter variety is normally planted in autumn or spring and is harvested by mid-summer.

Question 3.
What would be expected to happen if:
(a) GA₃ is applied to rice seedlings.
(b) Dividing cells stop differentiating.
(c) A rotten fruit gets mixed with unripe fruits.
Answer:
(a) Will exhibit intemode elongation and increase in height.
(b) If dividing cells stop differentiating, mass of undifferentiated cells is formed called callus.
(c) 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.

Question 4.
With reference to growth, define the following terms.
1. Differentiation.
2. Dedifferentiation.
3. Redifferentiation
Answer:
Differentiation, Dedifferentiation and Redifferentiation:
Differentiation: It is the conversion (maturation) of meristematic cells, to regain the power to divide under certain conditions.

Dedifferentiation: Permanent cells like parenchyma can revert back to meristematic activities (cell division) to form secondary meristern. This conversion is called Dedifferentiation.

Redifferentiation: If the secondary meristem divides to produce new cells, which further differentiate to form micelle cells, and once again lose the capacity to divide, then it is called as Redifferentiation.

1st PUC Biology Plant Growth and Development Five Marks Questions and Answers

Question 1.
Define growth, differentiation development, dedifferentiation, redifferentiation, determinate growth, meristem, and growth rate.
Answer:
Differentiation: It is the conversión (maturation) of meristematic cells, to regain the power to divide under certain conditions.

Dedifferentiation : Permanent cells like parenchyma can revert back to meristematic activities (cell division) to form secondary meristetn. This conversion is called Dedifferentiation.

Redifferentiation: If the secondary meristem divides to produce new cells, which further differentiate to form micelle cells, and once again lose the capacity to divide, then it is called as Redifferentiation.

Question 2.
List five main groups of natural plant growth regulators. Write a note on discovery, physiological functions and agricultural/horticultural applications of anyone of them.
Answer:

• It is also called as a stress hormone as it helps the plant to overcome adverse conditions like drought, flooding, injury etc.
• Synthesised in the fruits and leaves.
• First discovery by Addicott
• ABA Stimulates the formation of the abscission layer at the stalks of buds, leaves, petals and fruits and causes abscission.
• Can promote seed dormacy, bud dormancy.
• Stimulation stamatal closure.
• Can decrease RNA and Protein synthesis in leaves.

Question  3.
Which one of the plant growth regulators would you use if you are asked to:
(a) induce rooting in a twig.
Answer:
Auxin.

(b) quickly ripen a fruit.
Answer:
Ethylene.

(c) delay leaf senescence.
Answer:
Cytokinin.

(d) induce growth in axillary buds.
Answer:
Cytokinin.

(e) ‘bolt’ a rosette plant.
Answer:
Gibberellin.

(f) induce immediate stomatal closure in leaves.
Answer:
Abscisic acid (ABA).

Question 4.
Define photoperiodism and vernalisation. Describe their significances.
Answer:
Photoperiodism :
Plants, in order to flower, require a particular day length or light period called photoperiod and response of the plants to photoperiod in terms of flowering is called photoperiodism. Photoperiodism was first studied by W.W. Garner, and H.A. Allard.

Based on their photoperiodic responses, plants are classified into the following groups:

• Long Day Plants: These flower in photoperiod more than critical day length, eg : Wheat, oats etc.
• Short Day Plants: These flower in photoperiod less than critical day length. e.g: Tobacco, Chrysanthemums etc.
• Day Neutral Plants: These are the plants which are not influenced by the duration of light for their flowering. e.g: Tomato, cucumber, cotton etc.

Vernalisation :
Besides correct photoperiod, some plants require low temperature treatment for flowering. This treatment is known as vernalization.

Vernalization prevents precocious reproductive development late in the growing season, and enables the plant to have sufficient time to reach maturity.

Certain food plants like wheat, barley and  have two varieties called,

• Spring variety, and
• Winter variety.

The spring variety is planted in spring, and it completes the lifecycle before the growing season. The winter variety is normally planted in autumn or spring and is harvested by mid-summer.

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

Growth

• Growth can be defined as a permanent and irreversible change in the size, volume or weight of a plant or its parts.
• Plants show two types of growth, namely primary and secondary. Primary growth takes place at the stem or root tips, and it results in the growth in length. Secondary growth takes place due to the activity of cambium, and it results in the growth in thickness.
• In plants the growth is a localised phenomena.

Measurement of Growth:
Growth at the cellular level is mainly due to the increase in the amount of protoplasm. Since , it is difficult to measure the increase in protoplasm, one measures some quantity which is proportional to protoplasmic increase.

Growth is measured as increase in :
Fresh weight, dry weight, length or area, volume / size and cell number.

Growth Rate:

• The increase in growth per unit time is termed as growth rate.
• Rate of growth may be arithmetic or geometric. In arithmetic growth, one of the daughter cells formed by mitosis continues to divide, while the other undergoes differentiation and maturation.
• In Geometrical growth, both the daughter cells formed after mitosis, retain the in ability to divide.

Conditions for Growth:

• Nutrients provide the raw materials for the synthesis of protoplasm, and provide energy needed for various metabolic functions.
• Water is necessary to maintain turgidity of cells, and for functioning of enzymes.
• Oxygen is required for oxidation, and release of energy.
• Optimum temperature is required for plant – growth.
• Light influences the direction of growth.
• Mineral elements can influence the growth rate.

Phases of Growth:
Growth occurs in meristems. A meristematic cell passes through three phases or stages which are as follows.

• Cell Division: In this phase, the meristematic cells divide and redivide mitotically to form undifferentiated mass of cells.
• Cell Elongation: In this phase, newly formed cells increase in size by accumulating cytoplasmic material.
• Cell Saturation: In this phase, cells undergo structural and functional differentiation, into several cell types.

Growth Curve:
The curve obtained when the growth in size or weight or on entire plant or its individual parts is plotted against time is called growth curve. It is always ‘S’ or sigmoid in shape.
It shows three distinct phases namely.
(1) Lag phase.
(2) Log phase.
(3) Steady phase.
(1) Lag phase This is the initial stage where the growth rate is very slow. But it gradually increases with the time.

(2) Log phase In this phase, the rate of growth is very rapid. The plant shows high rate of growth, and reaches maximum height. Hence this phase is called exponential phase or grand period of growth.

(3) Steady phase or stationary phase This is the last phase in which plants shows no growth. Therefore the growth curve becomes almost horizontal.

Development :

• Development is considered as the sum of growth and differentiation. It is under the control of intrinsic and extrinsic factors.
• Intrinsic factors include intracellular or genetic factors.
• Extrinsic factors include light, temperature, water, oxygen and nutrients.

Differentiation, Dedifferentiation and Redifferentiation:

• Differentiation : It is the conversion (maturation) of meristematic cells, to regain the power to divide under certain conditions.
• Dedifferentiation: Permanent cells like parenchyma can revert back to meristematic activities (cell division) to form secondary meristem. This conversion is called Dedifferentiation.
• Redifferentiation : If the secondary meristem divides to produce new cells, which further differentiate to form micelle cells, and once again lose the capacity to divide, then it is called as Redifferentiation.

Growth Regulators / Hormones

• Hormones .can be defined as the organic substance produced naturally in higher plants which control the rate of growth, and other physiological functions.
• These phytohormones are produced in the stem tip and root tip of young leaves. These are translocated from the site of production to the site of their action through phloem.
• Hormones are classified as natural growth substances, and synthetic growth substances.

I. Natural Growth Substances:
These are naturally occurring in the plant body. They are of two types, namely:-
1. Growth Promoters :- Which promote growth e.g. Auxins, Gibberellins and Cytokinins.
2. Growth Retarders :- Which retard growth e.g. Ethylene and Abscissic Acid.

Auxins:

• Auxins were the first hormones to be discovered in plants.
• F.W. Went confirmed, and isolated the auxins from coleoptiles of Avena sativa.
• Chemically it is called lndole-3-Acetic. Acid and is derived from amino acid tryptophan.
• Auxins can stimulate cell division, cell elongation and cell maturation.
• It promotes Apical dominance.
• It initiates Root formation.
• Can promote parthenocarpy.
• Prevent premature fall of flowers, buds, and leaves.
• 2,4D, and 2,4,5T are used as selective weedicides.
• Promote phototrophic and hydrotropic movements.
• Promote xylem differentiation.

Gibberellins:

• Discovered by Kurasawa in paddy seedlings, while investigating the cause for Bakane disease.
• Yabuta, and Sumuki isolated gibberellins from the fungi Gibberella fuzikori.
• Gibberellins break genetic dwarfism in dwarf varieties of pea and beans.
• Can induce internode elongation, and early flowering in rosette plants like cabbage and cauli-flower. This is called bolting.
• Can break seed dormancy, and bud dormancy.
• Can induce parthenocarpic fruits.
• Gibberellins can substitute cold treatment i.e., can replace vernalisation.
• Can be used in inducing flowers even in off seasons in long day plants.

Cytokinins / Kinetins

• Discovered by Skoog and Miller
• Chemically these are 6-fur fury! amino purines.
• Synthesised in young fruits, leaves, buds, root tips and translocated through xylem.
• Cytokinins stimulates the cell division.
• Cytokinins prevent early ageing or senescence by stabilizing proteins and chlorophyll. This phenomenon is called Richmond – Lang effect,
• Cytokinins break seed dormancy and induce germination.

Abscisic Acid / Aba / Dormin

• It is also called as a stress hormone as it helps the plant to overcome the adverse conditions like drought, flooding, injury etc.
• Synthesised in the fruits and leaves.
• First discovered by Addicott
• ABA Stimulates the formation of abscission layer at the stalks of buds, leaves, petals and fruits and causes abscission.
• Can promote seed dormancy; and’ bud dormancy.
• Stimulates stomata! closure.
• Can decrease RNA and Protein synthesis in leaves.

Ethylene

• Only gaseous plant hormone.
• Product of metabolism of amino acid methionine.
• Ethylene is a fruit ripening agent.
• Promotes senescence of flowers, leaves and fruits.
• Initiates flowering in pine apple.

Photoperiodism :
Plants, in order to flower, require a particular day length or light period called photoperiod and response of the plants to photoperiod in terms of flowering is called photoperiodism. Photoperiodism was first studied by W.W. Garner, and H.A. Allard.
Based on their photoperiodic responses, plants are classified into the following groups:

• Long Day Plants: These flower in photoperiod more than critical day length, eg : Wheat, oats etc.
• Short Day Plants: These flower in photoperiod less than critical day length.
  e.g: Tobacco, Chrysanthemums etc.
• Day Neutral Plants: These are the plants which are not influenced by the duration of light for their flowering. e.g: Tomato, cucumber, cotton etc.

Vernalisation :
Besides correct photoperiod, some plants require low temperature treatment for flowering. This treatment is known as vernalization.
Vernalization prevents precocious reproductive development late in the growing season, and enables the plant to have sufficient time to reach maturity.

Certain food plants like wheat, barley and have two varieties called,
(i) Spring variety, and
(ii) Winter variety.
The spring variety is planted in spring, and it completes the lifecycle before the growing season. The winter variety is normally planted in autumn or spring and is harvested by mid-summer

1st PUC Biology Question Bank with Answers