Plant Growth and Development Practice Questions - DPP for NEET

 Page 1


Solution
1. (c)
A. E.Kurosawa (1926) reported the appearance
of symptoms of the disease in rice seedlings
when they were treated with sterile filtrates
of the fungus. The active substances were
later identified as gibberellic acid.
B. Miller and Skoog identified andcrystallised the
cytokinesis promoting active substance that
they termed kinetin.
C. H.H. Cousins (1910) confirmed the release
of a volatile substance from ripened oranges
that hastened the ripening of stored unripened
bananas. Later this volatile substance was
identified as ethylene, a gaseous PGR.
D. Auxin was isolated by F.W. Went from tips
of coleoptiles of oat seedlings.
2. (c)
Phytohormones can be broadly classified into two
groups based on their functions in a living plant
body - growth promoters and growth inhibitors.
Auxin, gibberellin and cytokinin are growth
promoters and ethylene and abscissic acid (ABA)
are growth inhibitors.
Functions of growth promoters - I, II, III, IV , V , VI, VII
Functions of growth inhibitors - VIII, IX
3. (c)
In the given graph of geometric growth rate, (c)
is the correct answer. According to this graph,
with limited supply of nutrients, the growth rate
slows down leading to stationary phase.
4. (c)
(i) Absolute growth rate (AGR) is actual growth
per unit time.
AGR of leaf A = 10 – 5 = 5
AGR of leaf B = 55 – 50 = 5
(ii) Relative growth rate (RGR) is the growth
per unit time as percentage of initial size.
RGR of leaf 
5
A 100 100%
5
? ? ?
RGR of leaf 
5
B 100 10%
50
? ? ?
5. (b)
Relative growth rate is the measure of the ability
of the plant to produce new plant material.
Growth = 19 – 5 = 14 cm
Period = 7 days
Growth rate = 14/7 = 2 cm/day
Relative growth rate = 2/5 × 100 = 40%
6. (d)
All statements are correct.
7. (d)
Development includes all changes that an
organism goes through during its life cycle from
germination of the seed to senescence. The
correct sequence of the developmental process
in a plant cell is:
Cell division ? Differentiation ? Maturation ?
Senescence
Cell division involves plasmatic growth.
Differentiation is a process in which cells undergo
few to major structural changes both in their cell
walls and protoplasm. Maturation is the process
that a living thing goes through as it ages and
becomes ripe or fully developed. Senescence is
the stage in the life history of an individual when
the rate of metabolic activities declines that leads
to ageing and then eventually death.
8. (c)
(iii) In arithmetic growth, following mitotic cell
division, only one daughter cell continues to
divide while the other differentiates and
matures.
(iv) In geometrical growth, both the progeny
cells following mitotic cell division retain the
ability to divide and continue to do so.
(vi) Geometrical growth, is typical for all cells,
tissues and organs of a plant.
9. (b)
Experiment done by Charles Darwin and his son
on plant phototropism shows that the tip of the
coleoptile is the light receptor of the plant that
caused the bending of the entire coleoptile towards
the light source.
10. (b)
Ethylene is a gaseous hormone. It is a natural
plant hormone which affects the growth,
development, ripening, and senescence (aging)
of all plants. It is normally produced in small
quantities by most fruits and vegetables. Many
fruits produce larger quantities of ethylene and
respond with uniform ripening when exposed to
an external source of ethylene.
11. (a)
Kinetin (cytokinin) is a modified form of adenine,
a purine.
Page 2


Solution
1. (c)
A. E.Kurosawa (1926) reported the appearance
of symptoms of the disease in rice seedlings
when they were treated with sterile filtrates
of the fungus. The active substances were
later identified as gibberellic acid.
B. Miller and Skoog identified andcrystallised the
cytokinesis promoting active substance that
they termed kinetin.
C. H.H. Cousins (1910) confirmed the release
of a volatile substance from ripened oranges
that hastened the ripening of stored unripened
bananas. Later this volatile substance was
identified as ethylene, a gaseous PGR.
D. Auxin was isolated by F.W. Went from tips
of coleoptiles of oat seedlings.
2. (c)
Phytohormones can be broadly classified into two
groups based on their functions in a living plant
body - growth promoters and growth inhibitors.
Auxin, gibberellin and cytokinin are growth
promoters and ethylene and abscissic acid (ABA)
are growth inhibitors.
Functions of growth promoters - I, II, III, IV , V , VI, VII
Functions of growth inhibitors - VIII, IX
3. (c)
In the given graph of geometric growth rate, (c)
is the correct answer. According to this graph,
with limited supply of nutrients, the growth rate
slows down leading to stationary phase.
4. (c)
(i) Absolute growth rate (AGR) is actual growth
per unit time.
AGR of leaf A = 10 – 5 = 5
AGR of leaf B = 55 – 50 = 5
(ii) Relative growth rate (RGR) is the growth
per unit time as percentage of initial size.
RGR of leaf 
5
A 100 100%
5
? ? ?
RGR of leaf 
5
B 100 10%
50
? ? ?
5. (b)
Relative growth rate is the measure of the ability
of the plant to produce new plant material.
Growth = 19 – 5 = 14 cm
Period = 7 days
Growth rate = 14/7 = 2 cm/day
Relative growth rate = 2/5 × 100 = 40%
6. (d)
All statements are correct.
7. (d)
Development includes all changes that an
organism goes through during its life cycle from
germination of the seed to senescence. The
correct sequence of the developmental process
in a plant cell is:
Cell division ? Differentiation ? Maturation ?
Senescence
Cell division involves plasmatic growth.
Differentiation is a process in which cells undergo
few to major structural changes both in their cell
walls and protoplasm. Maturation is the process
that a living thing goes through as it ages and
becomes ripe or fully developed. Senescence is
the stage in the life history of an individual when
the rate of metabolic activities declines that leads
to ageing and then eventually death.
8. (c)
(iii) In arithmetic growth, following mitotic cell
division, only one daughter cell continues to
divide while the other differentiates and
matures.
(iv) In geometrical growth, both the progeny
cells following mitotic cell division retain the
ability to divide and continue to do so.
(vi) Geometrical growth, is typical for all cells,
tissues and organs of a plant.
9. (b)
Experiment done by Charles Darwin and his son
on plant phototropism shows that the tip of the
coleoptile is the light receptor of the plant that
caused the bending of the entire coleoptile towards
the light source.
10. (b)
Ethylene is a gaseous hormone. It is a natural
plant hormone which affects the growth,
development, ripening, and senescence (aging)
of all plants. It is normally produced in small
quantities by most fruits and vegetables. Many
fruits produce larger quantities of ethylene and
respond with uniform ripening when exposed to
an external source of ethylene.
11. (a)
Kinetin (cytokinin) is a modified form of adenine,
a purine.
12. (b)
In conifers, gibberellin (GA) has been found to
cause quicker early growth so that maturity is
reached early. It is useful for obtaining early and
quicker yield of economically important seeds.
13. (c)
Germinating barley grains produce more malt
when provided with GA
3
 probably by forming
higher quantities of a -amylase and other
hydrolytic enzymes.
14. (d)
(I) Measurement and the comparison of total
growth per unit time is called the absolute
growth rate.
(II) The growth of the given system per unit time
expressed on a common basis, e.g., per unit
initial parameter is called the relative
growth rate.
15. (a)
Both statements are correct.
16. (a)
The climacteric in plants is a stage of fruit ripening
associated with increased ethylene production and
a rise in cellular respiration. Apples, bananas,
melons, apricots, tomatoes (among others) are
climacteric fruit. Citrus, grapes, strawberries are
non-climacteric (they ripen without ethylene and
respiration bursts).
17. (b)
(II) Difference in shapes of leaves produced in
air and those produced in water in buttercup
represent the heterophyllous development
due to environment.
18. (a)
Abscissic acid (ABA), also known as abscisin II
and dormin, is usually found in vascular plants,
some fungi and some green algae. It is a
multipurpose plant hormone which acts as an
inhibitor because it opposes the growth of
promoting effect of auxins, GA and cytokinins,
thus keep their activity under control. ABA is also
known as stress hormone because it is produced
under conditions of stress and causes partial
closure of stomata under drought and thus acts
as antitranspirants.
19. (d)
Ethylene promotes abscission and senescence of
leaves, flowers etc.
20. (a)
Both statements are correct.
21. (b)
Ethephon is the compound used to supply
ethylene. It is readily absorbed in aqueous solution
and transported within the plant and it releases
ethylene slowly. Ethephon hastens fruit ripening
in tomatoes and apples. It accelerates abscission
of flowers and fruits in cotton, cherry, walnut,
etc.
22. (d)
Abscissic acid (ABA), also known as abscisin II
and dormin. It is usually found in vascular plants,
some fungi and some green algae. It acts as an
inhibitor because it opposes the growth of
promoting effect of auxins, GA and cytokinins,
thus keep their activity under control. Leaf
abscission, fruit fall and dormancy occurs due to
abscissic acid.
23. (b)
In guard cells, the plant hormone abscisic acid
(ABA) inhibits stomatal opening and induces
stomatal closure through the coordinated
regulation of ion transport.
24. (a)
ABA counteracts many effects of GA such as
induction of hydrolases and ?-amylase in barley
seedlings.
25. (c)
(v) The cells in meristematic phase region are
rich in protoplasm, possess large conspicuous
nuclei and cell walls are primary in nature.
(vi) Increased vacuolation, cell enlargement and
new cell wall deposition are the characteristics
of the cells in phase of elongation region.
26. (a)
(i) On plotting the length of the organ against
time, a linear curve is obtained.
(ii) Mathematically, it is expressed as L
t 
= L
0
 + rt.
Both these statements are correct
regarding arithmetic growth.
27. (d)
All statements are correct.
Page 3


Solution
1. (c)
A. E.Kurosawa (1926) reported the appearance
of symptoms of the disease in rice seedlings
when they were treated with sterile filtrates
of the fungus. The active substances were
later identified as gibberellic acid.
B. Miller and Skoog identified andcrystallised the
cytokinesis promoting active substance that
they termed kinetin.
C. H.H. Cousins (1910) confirmed the release
of a volatile substance from ripened oranges
that hastened the ripening of stored unripened
bananas. Later this volatile substance was
identified as ethylene, a gaseous PGR.
D. Auxin was isolated by F.W. Went from tips
of coleoptiles of oat seedlings.
2. (c)
Phytohormones can be broadly classified into two
groups based on their functions in a living plant
body - growth promoters and growth inhibitors.
Auxin, gibberellin and cytokinin are growth
promoters and ethylene and abscissic acid (ABA)
are growth inhibitors.
Functions of growth promoters - I, II, III, IV , V , VI, VII
Functions of growth inhibitors - VIII, IX
3. (c)
In the given graph of geometric growth rate, (c)
is the correct answer. According to this graph,
with limited supply of nutrients, the growth rate
slows down leading to stationary phase.
4. (c)
(i) Absolute growth rate (AGR) is actual growth
per unit time.
AGR of leaf A = 10 – 5 = 5
AGR of leaf B = 55 – 50 = 5
(ii) Relative growth rate (RGR) is the growth
per unit time as percentage of initial size.
RGR of leaf 
5
A 100 100%
5
? ? ?
RGR of leaf 
5
B 100 10%
50
? ? ?
5. (b)
Relative growth rate is the measure of the ability
of the plant to produce new plant material.
Growth = 19 – 5 = 14 cm
Period = 7 days
Growth rate = 14/7 = 2 cm/day
Relative growth rate = 2/5 × 100 = 40%
6. (d)
All statements are correct.
7. (d)
Development includes all changes that an
organism goes through during its life cycle from
germination of the seed to senescence. The
correct sequence of the developmental process
in a plant cell is:
Cell division ? Differentiation ? Maturation ?
Senescence
Cell division involves plasmatic growth.
Differentiation is a process in which cells undergo
few to major structural changes both in their cell
walls and protoplasm. Maturation is the process
that a living thing goes through as it ages and
becomes ripe or fully developed. Senescence is
the stage in the life history of an individual when
the rate of metabolic activities declines that leads
to ageing and then eventually death.
8. (c)
(iii) In arithmetic growth, following mitotic cell
division, only one daughter cell continues to
divide while the other differentiates and
matures.
(iv) In geometrical growth, both the progeny
cells following mitotic cell division retain the
ability to divide and continue to do so.
(vi) Geometrical growth, is typical for all cells,
tissues and organs of a plant.
9. (b)
Experiment done by Charles Darwin and his son
on plant phototropism shows that the tip of the
coleoptile is the light receptor of the plant that
caused the bending of the entire coleoptile towards
the light source.
10. (b)
Ethylene is a gaseous hormone. It is a natural
plant hormone which affects the growth,
development, ripening, and senescence (aging)
of all plants. It is normally produced in small
quantities by most fruits and vegetables. Many
fruits produce larger quantities of ethylene and
respond with uniform ripening when exposed to
an external source of ethylene.
11. (a)
Kinetin (cytokinin) is a modified form of adenine,
a purine.
12. (b)
In conifers, gibberellin (GA) has been found to
cause quicker early growth so that maturity is
reached early. It is useful for obtaining early and
quicker yield of economically important seeds.
13. (c)
Germinating barley grains produce more malt
when provided with GA
3
 probably by forming
higher quantities of a -amylase and other
hydrolytic enzymes.
14. (d)
(I) Measurement and the comparison of total
growth per unit time is called the absolute
growth rate.
(II) The growth of the given system per unit time
expressed on a common basis, e.g., per unit
initial parameter is called the relative
growth rate.
15. (a)
Both statements are correct.
16. (a)
The climacteric in plants is a stage of fruit ripening
associated with increased ethylene production and
a rise in cellular respiration. Apples, bananas,
melons, apricots, tomatoes (among others) are
climacteric fruit. Citrus, grapes, strawberries are
non-climacteric (they ripen without ethylene and
respiration bursts).
17. (b)
(II) Difference in shapes of leaves produced in
air and those produced in water in buttercup
represent the heterophyllous development
due to environment.
18. (a)
Abscissic acid (ABA), also known as abscisin II
and dormin, is usually found in vascular plants,
some fungi and some green algae. It is a
multipurpose plant hormone which acts as an
inhibitor because it opposes the growth of
promoting effect of auxins, GA and cytokinins,
thus keep their activity under control. ABA is also
known as stress hormone because it is produced
under conditions of stress and causes partial
closure of stomata under drought and thus acts
as antitranspirants.
19. (d)
Ethylene promotes abscission and senescence of
leaves, flowers etc.
20. (a)
Both statements are correct.
21. (b)
Ethephon is the compound used to supply
ethylene. It is readily absorbed in aqueous solution
and transported within the plant and it releases
ethylene slowly. Ethephon hastens fruit ripening
in tomatoes and apples. It accelerates abscission
of flowers and fruits in cotton, cherry, walnut,
etc.
22. (d)
Abscissic acid (ABA), also known as abscisin II
and dormin. It is usually found in vascular plants,
some fungi and some green algae. It acts as an
inhibitor because it opposes the growth of
promoting effect of auxins, GA and cytokinins,
thus keep their activity under control. Leaf
abscission, fruit fall and dormancy occurs due to
abscissic acid.
23. (b)
In guard cells, the plant hormone abscisic acid
(ABA) inhibits stomatal opening and induces
stomatal closure through the coordinated
regulation of ion transport.
24. (a)
ABA counteracts many effects of GA such as
induction of hydrolases and ?-amylase in barley
seedlings.
25. (c)
(v) The cells in meristematic phase region are
rich in protoplasm, possess large conspicuous
nuclei and cell walls are primary in nature.
(vi) Increased vacuolation, cell enlargement and
new cell wall deposition are the characteristics
of the cells in phase of elongation region.
26. (a)
(i) On plotting the length of the organ against
time, a linear curve is obtained.
(ii) Mathematically, it is expressed as L
t 
= L
0
 + rt.
Both these statements are correct
regarding arithmetic growth.
27. (d)
All statements are correct.
28. (b)
(iv) Skoog and Miller identified and crystallised
the cytokinesis promoting active substance
that they termed kinetin.
(v) Inhibitor-B, abscission II and dormin were
chemically identical and named as abscisic
acid (ABA).
29. (d)
All the given statements are the characteristics
of growth of an organism. Growth can be
defined as an irreversible permanent increase
in size of an organ or its parts or even of an
individual cell.
30. (d)
Water does not oxidize glucose to provide energy.
It maintains the turgidity of growing cells and
provides medium for enzymatic reactions.
31. (a)
IAA and IBM are natural auxins but NAA, 2, 4 -
D and 2, 4, 5 T are synthetic auxins.
32. (c)
Ethylene promotes senescence and abscission of
plant organs especially of leaves and flowers. It
enhances the respiration rate during fruit ripening.
Ethylene is also used to initiate flowering and for
synchronising fruit-set in pineapples. It also
induces flowering in mango.
33. (d)
All the given statements regarding ethephon are
correct. Ethephon is a synthetic plant growth
regulator that induces flowering and abscission
by promoting the release of ethylene and has been
used to cause early ripening (as of apples on the
tree).
34. (b)
Gibberellin helps in cell growth of stem, leaves
and other aerial parts.
35. (c)
The plant growth regulators (PGRs) are small,
simple molecule of diverse chemical composition.
They could be indole compounds (indole-3-acetic
acid, (IAA, IBA); adenine derivatives (N
6
-
furfurylamino purine, kinetin) derivatives of
carotenoids (abscisic acid); terpenes (gibberellic
acid, GA
3
) or gases (ethylene, C
2
H
4
).
36. (b)
(II) The cells proximal to the meristematic zone
represent the phase of elongation.
37. (a)
Both statements are correct.
38. (b)
(II) This act leading to maturation is termed as
differentiation.
39. (b)
IBA (indole butyric acid) is a natural plant hormone
in the auxin family and is an ingredient in many
commercial horticultural plant rooting products. It is
used for stimulating plant growth and root formation.
40. (c)
(I) Difference in shapes of leaves produced in
air and those produced in water in buttercup.
41. (c)
Flowering in pineapple is promoted by NAA
(Naphthalene acetic acid). NAA is a synthetic
plant hormone in the auxin family. NAA and 2, 4,
D are synthetic auxin plant hormones. All these
auxins have been used extensively in agricultural
and horticultural practices.
42. (a)
Indole compounds (e.g, IAA, IBA) help to prevent
fruit and leaf drop at early stage but promote the
abscission of older mature leaves and fruits. Indole
is an aromatic heterocyclic organic compound. It
has a bicyclic structure, consisting of a six-
membered benzene ring fused to a five-membered
nitrogencontaining pyrrole ring.
43. (b)
(II) ABA stimulates the closure of stomata and
increases the tolerance of plants to various
kinds of stresses.
44. (b)
(i) Spraying juvenile conifers with Gibberellins
hastens the maturity period, thus leading to
early seed production.
(ii) Gibberellins promotes bolting in beet,
cabbages and many plants with rosette habit.
(iii) Cytokinins helps to produce new leaves,
chloroplasts in leaves, lateral shoot growth
and adventitious shoot formation.
(iv) The ability of Gibberellins to cause an
increase in length of axis is used to increase
the length of grapes stalks.
45. (d)
All statements are correct.
Page 4


Solution
1. (c)
A. E.Kurosawa (1926) reported the appearance
of symptoms of the disease in rice seedlings
when they were treated with sterile filtrates
of the fungus. The active substances were
later identified as gibberellic acid.
B. Miller and Skoog identified andcrystallised the
cytokinesis promoting active substance that
they termed kinetin.
C. H.H. Cousins (1910) confirmed the release
of a volatile substance from ripened oranges
that hastened the ripening of stored unripened
bananas. Later this volatile substance was
identified as ethylene, a gaseous PGR.
D. Auxin was isolated by F.W. Went from tips
of coleoptiles of oat seedlings.
2. (c)
Phytohormones can be broadly classified into two
groups based on their functions in a living plant
body - growth promoters and growth inhibitors.
Auxin, gibberellin and cytokinin are growth
promoters and ethylene and abscissic acid (ABA)
are growth inhibitors.
Functions of growth promoters - I, II, III, IV , V , VI, VII
Functions of growth inhibitors - VIII, IX
3. (c)
In the given graph of geometric growth rate, (c)
is the correct answer. According to this graph,
with limited supply of nutrients, the growth rate
slows down leading to stationary phase.
4. (c)
(i) Absolute growth rate (AGR) is actual growth
per unit time.
AGR of leaf A = 10 – 5 = 5
AGR of leaf B = 55 – 50 = 5
(ii) Relative growth rate (RGR) is the growth
per unit time as percentage of initial size.
RGR of leaf 
5
A 100 100%
5
? ? ?
RGR of leaf 
5
B 100 10%
50
? ? ?
5. (b)
Relative growth rate is the measure of the ability
of the plant to produce new plant material.
Growth = 19 – 5 = 14 cm
Period = 7 days
Growth rate = 14/7 = 2 cm/day
Relative growth rate = 2/5 × 100 = 40%
6. (d)
All statements are correct.
7. (d)
Development includes all changes that an
organism goes through during its life cycle from
germination of the seed to senescence. The
correct sequence of the developmental process
in a plant cell is:
Cell division ? Differentiation ? Maturation ?
Senescence
Cell division involves plasmatic growth.
Differentiation is a process in which cells undergo
few to major structural changes both in their cell
walls and protoplasm. Maturation is the process
that a living thing goes through as it ages and
becomes ripe or fully developed. Senescence is
the stage in the life history of an individual when
the rate of metabolic activities declines that leads
to ageing and then eventually death.
8. (c)
(iii) In arithmetic growth, following mitotic cell
division, only one daughter cell continues to
divide while the other differentiates and
matures.
(iv) In geometrical growth, both the progeny
cells following mitotic cell division retain the
ability to divide and continue to do so.
(vi) Geometrical growth, is typical for all cells,
tissues and organs of a plant.
9. (b)
Experiment done by Charles Darwin and his son
on plant phototropism shows that the tip of the
coleoptile is the light receptor of the plant that
caused the bending of the entire coleoptile towards
the light source.
10. (b)
Ethylene is a gaseous hormone. It is a natural
plant hormone which affects the growth,
development, ripening, and senescence (aging)
of all plants. It is normally produced in small
quantities by most fruits and vegetables. Many
fruits produce larger quantities of ethylene and
respond with uniform ripening when exposed to
an external source of ethylene.
11. (a)
Kinetin (cytokinin) is a modified form of adenine,
a purine.
12. (b)
In conifers, gibberellin (GA) has been found to
cause quicker early growth so that maturity is
reached early. It is useful for obtaining early and
quicker yield of economically important seeds.
13. (c)
Germinating barley grains produce more malt
when provided with GA
3
 probably by forming
higher quantities of a -amylase and other
hydrolytic enzymes.
14. (d)
(I) Measurement and the comparison of total
growth per unit time is called the absolute
growth rate.
(II) The growth of the given system per unit time
expressed on a common basis, e.g., per unit
initial parameter is called the relative
growth rate.
15. (a)
Both statements are correct.
16. (a)
The climacteric in plants is a stage of fruit ripening
associated with increased ethylene production and
a rise in cellular respiration. Apples, bananas,
melons, apricots, tomatoes (among others) are
climacteric fruit. Citrus, grapes, strawberries are
non-climacteric (they ripen without ethylene and
respiration bursts).
17. (b)
(II) Difference in shapes of leaves produced in
air and those produced in water in buttercup
represent the heterophyllous development
due to environment.
18. (a)
Abscissic acid (ABA), also known as abscisin II
and dormin, is usually found in vascular plants,
some fungi and some green algae. It is a
multipurpose plant hormone which acts as an
inhibitor because it opposes the growth of
promoting effect of auxins, GA and cytokinins,
thus keep their activity under control. ABA is also
known as stress hormone because it is produced
under conditions of stress and causes partial
closure of stomata under drought and thus acts
as antitranspirants.
19. (d)
Ethylene promotes abscission and senescence of
leaves, flowers etc.
20. (a)
Both statements are correct.
21. (b)
Ethephon is the compound used to supply
ethylene. It is readily absorbed in aqueous solution
and transported within the plant and it releases
ethylene slowly. Ethephon hastens fruit ripening
in tomatoes and apples. It accelerates abscission
of flowers and fruits in cotton, cherry, walnut,
etc.
22. (d)
Abscissic acid (ABA), also known as abscisin II
and dormin. It is usually found in vascular plants,
some fungi and some green algae. It acts as an
inhibitor because it opposes the growth of
promoting effect of auxins, GA and cytokinins,
thus keep their activity under control. Leaf
abscission, fruit fall and dormancy occurs due to
abscissic acid.
23. (b)
In guard cells, the plant hormone abscisic acid
(ABA) inhibits stomatal opening and induces
stomatal closure through the coordinated
regulation of ion transport.
24. (a)
ABA counteracts many effects of GA such as
induction of hydrolases and ?-amylase in barley
seedlings.
25. (c)
(v) The cells in meristematic phase region are
rich in protoplasm, possess large conspicuous
nuclei and cell walls are primary in nature.
(vi) Increased vacuolation, cell enlargement and
new cell wall deposition are the characteristics
of the cells in phase of elongation region.
26. (a)
(i) On plotting the length of the organ against
time, a linear curve is obtained.
(ii) Mathematically, it is expressed as L
t 
= L
0
 + rt.
Both these statements are correct
regarding arithmetic growth.
27. (d)
All statements are correct.
28. (b)
(iv) Skoog and Miller identified and crystallised
the cytokinesis promoting active substance
that they termed kinetin.
(v) Inhibitor-B, abscission II and dormin were
chemically identical and named as abscisic
acid (ABA).
29. (d)
All the given statements are the characteristics
of growth of an organism. Growth can be
defined as an irreversible permanent increase
in size of an organ or its parts or even of an
individual cell.
30. (d)
Water does not oxidize glucose to provide energy.
It maintains the turgidity of growing cells and
provides medium for enzymatic reactions.
31. (a)
IAA and IBM are natural auxins but NAA, 2, 4 -
D and 2, 4, 5 T are synthetic auxins.
32. (c)
Ethylene promotes senescence and abscission of
plant organs especially of leaves and flowers. It
enhances the respiration rate during fruit ripening.
Ethylene is also used to initiate flowering and for
synchronising fruit-set in pineapples. It also
induces flowering in mango.
33. (d)
All the given statements regarding ethephon are
correct. Ethephon is a synthetic plant growth
regulator that induces flowering and abscission
by promoting the release of ethylene and has been
used to cause early ripening (as of apples on the
tree).
34. (b)
Gibberellin helps in cell growth of stem, leaves
and other aerial parts.
35. (c)
The plant growth regulators (PGRs) are small,
simple molecule of diverse chemical composition.
They could be indole compounds (indole-3-acetic
acid, (IAA, IBA); adenine derivatives (N
6
-
furfurylamino purine, kinetin) derivatives of
carotenoids (abscisic acid); terpenes (gibberellic
acid, GA
3
) or gases (ethylene, C
2
H
4
).
36. (b)
(II) The cells proximal to the meristematic zone
represent the phase of elongation.
37. (a)
Both statements are correct.
38. (b)
(II) This act leading to maturation is termed as
differentiation.
39. (b)
IBA (indole butyric acid) is a natural plant hormone
in the auxin family and is an ingredient in many
commercial horticultural plant rooting products. It is
used for stimulating plant growth and root formation.
40. (c)
(I) Difference in shapes of leaves produced in
air and those produced in water in buttercup.
41. (c)
Flowering in pineapple is promoted by NAA
(Naphthalene acetic acid). NAA is a synthetic
plant hormone in the auxin family. NAA and 2, 4,
D are synthetic auxin plant hormones. All these
auxins have been used extensively in agricultural
and horticultural practices.
42. (a)
Indole compounds (e.g, IAA, IBA) help to prevent
fruit and leaf drop at early stage but promote the
abscission of older mature leaves and fruits. Indole
is an aromatic heterocyclic organic compound. It
has a bicyclic structure, consisting of a six-
membered benzene ring fused to a five-membered
nitrogencontaining pyrrole ring.
43. (b)
(II) ABA stimulates the closure of stomata and
increases the tolerance of plants to various
kinds of stresses.
44. (b)
(i) Spraying juvenile conifers with Gibberellins
hastens the maturity period, thus leading to
early seed production.
(ii) Gibberellins promotes bolting in beet,
cabbages and many plants with rosette habit.
(iii) Cytokinins helps to produce new leaves,
chloroplasts in leaves, lateral shoot growth
and adventitious shoot formation.
(iv) The ability of Gibberellins to cause an
increase in length of axis is used to increase
the length of grapes stalks.
45. (d)
All statements are correct.
46. (c)
Growth is defined as a permanent or irreversible
increase in the dry weight, size, mass or volume
of a cell, organ or organism. Generally, growth is
accompanied by metabolic processes (both
anabolic and catabolic), that occur at the expense
of energy.
47. (c)
Reason : Plants have hormones called
phytohormones. These can increase the reaction
rate and can also decrease the rate of reaction.
They can either promote growth or be inhibitory
in action.
48. (a)
Plant growth is unique because plants retain the
capacity for unlimited growth throughout their life.
This ability of the plants is due to the presence of
meristems at certain locations in their body. The
cells of such meristems have the capacity to divide
and self-perpetuate. The product, however, soon
loses the capacity to divide and such cells make
up the plant body. This form of growth wherein
new cells are always being added to the plant body
by the activity of the meristem is called the open
form of growth.
49. (a)
Arithmetic growth is a type of growth in which
the rate of growth is constant and increase in
growth occurs in arithmetic progression i.e., 2, 4,
6, 8 etc. Here after mitosis, only one daughter
cell continues to divide and other takes part in
differentiation and maturation. Here a linear curve
is obtained with positive value.
50. (a)
The rate of growth can be measured by an
increase in size or area of an organ of the plant
like leaf, flower, fruit etc. in a unit time. The rate
of growth is also called efficiency index.
51. (c)
Differentiation is maturation of cells derived from
optical meristems of root and shoot. It is applied
to the qualitative differences between cells, tissues
and organs. During differentiation cell undergoes
few to major anatomical and physiological
changes both in their cell walls and protoplasm.
For example, to form tracheary element, the cells
would lose their protoplasm.
52. (c)
In different phases of growth, plants follow
different pathways and form different kinds of
structures in response to environment. The ability
to change under the influence of internal or
external stimuli is called plasticity, e.g.,
heterophylly in cotton, coriander and larkspur.
Occurence of different types of structures on
same plant in different growth phases or under
different environment conditions is known as
heterophylly.
53. (c)
During mid- 1960s, three independent researches
reported the purification and chemical
characterization of three different kinds of
inhibiters : inhibitor - B, abscission II and dormin.
Later all the three were proven to be chemically
identical. It was named abscisic acid (ABA).
ABA plays an important role in seed development,
maturation & dormancy.
54. (a)
Auxin is a weakly acidic hormone having an
unsaturated ring structure and promotes cell
elongation especially in shoots. Auxins was first
isolated from human urine. Auxins like IAA and
IBA have been isolated from plants. NAA and 2,
4 - D are synthetic auxins.
55. (d)
Auxins inhibit the growth of axillary buds and
promote apical dominance. It induces
parthenocarpic development of fruits and such
fruits are seedless and auxin is also responsible
for phototropism and geotropisms. Ripening and
maturity of fruits are related to ethylene.
56. (c)
(iii) Cytokinins helps to produce new leaves,
chloroplasts in leaves, lateral shoot growth
and adventitious shoot formation.
(v) Auxin help to initiate rooting in stem cuttings.
(vi) Auxins promote flowering e.g. in pineapples.
57. (c)
(i) Cytokinins have specific effects on
cytokinesis.
(ii) Cytokinins is a modified form of adenine.
(iii) Kinetin does not occur naturally in plants.
(iv) Zeatin is isolation from coconut milk.
Page 5


Solution
1. (c)
A. E.Kurosawa (1926) reported the appearance
of symptoms of the disease in rice seedlings
when they were treated with sterile filtrates
of the fungus. The active substances were
later identified as gibberellic acid.
B. Miller and Skoog identified andcrystallised the
cytokinesis promoting active substance that
they termed kinetin.
C. H.H. Cousins (1910) confirmed the release
of a volatile substance from ripened oranges
that hastened the ripening of stored unripened
bananas. Later this volatile substance was
identified as ethylene, a gaseous PGR.
D. Auxin was isolated by F.W. Went from tips
of coleoptiles of oat seedlings.
2. (c)
Phytohormones can be broadly classified into two
groups based on their functions in a living plant
body - growth promoters and growth inhibitors.
Auxin, gibberellin and cytokinin are growth
promoters and ethylene and abscissic acid (ABA)
are growth inhibitors.
Functions of growth promoters - I, II, III, IV , V , VI, VII
Functions of growth inhibitors - VIII, IX
3. (c)
In the given graph of geometric growth rate, (c)
is the correct answer. According to this graph,
with limited supply of nutrients, the growth rate
slows down leading to stationary phase.
4. (c)
(i) Absolute growth rate (AGR) is actual growth
per unit time.
AGR of leaf A = 10 – 5 = 5
AGR of leaf B = 55 – 50 = 5
(ii) Relative growth rate (RGR) is the growth
per unit time as percentage of initial size.
RGR of leaf 
5
A 100 100%
5
? ? ?
RGR of leaf 
5
B 100 10%
50
? ? ?
5. (b)
Relative growth rate is the measure of the ability
of the plant to produce new plant material.
Growth = 19 – 5 = 14 cm
Period = 7 days
Growth rate = 14/7 = 2 cm/day
Relative growth rate = 2/5 × 100 = 40%
6. (d)
All statements are correct.
7. (d)
Development includes all changes that an
organism goes through during its life cycle from
germination of the seed to senescence. The
correct sequence of the developmental process
in a plant cell is:
Cell division ? Differentiation ? Maturation ?
Senescence
Cell division involves plasmatic growth.
Differentiation is a process in which cells undergo
few to major structural changes both in their cell
walls and protoplasm. Maturation is the process
that a living thing goes through as it ages and
becomes ripe or fully developed. Senescence is
the stage in the life history of an individual when
the rate of metabolic activities declines that leads
to ageing and then eventually death.
8. (c)
(iii) In arithmetic growth, following mitotic cell
division, only one daughter cell continues to
divide while the other differentiates and
matures.
(iv) In geometrical growth, both the progeny
cells following mitotic cell division retain the
ability to divide and continue to do so.
(vi) Geometrical growth, is typical for all cells,
tissues and organs of a plant.
9. (b)
Experiment done by Charles Darwin and his son
on plant phototropism shows that the tip of the
coleoptile is the light receptor of the plant that
caused the bending of the entire coleoptile towards
the light source.
10. (b)
Ethylene is a gaseous hormone. It is a natural
plant hormone which affects the growth,
development, ripening, and senescence (aging)
of all plants. It is normally produced in small
quantities by most fruits and vegetables. Many
fruits produce larger quantities of ethylene and
respond with uniform ripening when exposed to
an external source of ethylene.
11. (a)
Kinetin (cytokinin) is a modified form of adenine,
a purine.
12. (b)
In conifers, gibberellin (GA) has been found to
cause quicker early growth so that maturity is
reached early. It is useful for obtaining early and
quicker yield of economically important seeds.
13. (c)
Germinating barley grains produce more malt
when provided with GA
3
 probably by forming
higher quantities of a -amylase and other
hydrolytic enzymes.
14. (d)
(I) Measurement and the comparison of total
growth per unit time is called the absolute
growth rate.
(II) The growth of the given system per unit time
expressed on a common basis, e.g., per unit
initial parameter is called the relative
growth rate.
15. (a)
Both statements are correct.
16. (a)
The climacteric in plants is a stage of fruit ripening
associated with increased ethylene production and
a rise in cellular respiration. Apples, bananas,
melons, apricots, tomatoes (among others) are
climacteric fruit. Citrus, grapes, strawberries are
non-climacteric (they ripen without ethylene and
respiration bursts).
17. (b)
(II) Difference in shapes of leaves produced in
air and those produced in water in buttercup
represent the heterophyllous development
due to environment.
18. (a)
Abscissic acid (ABA), also known as abscisin II
and dormin, is usually found in vascular plants,
some fungi and some green algae. It is a
multipurpose plant hormone which acts as an
inhibitor because it opposes the growth of
promoting effect of auxins, GA and cytokinins,
thus keep their activity under control. ABA is also
known as stress hormone because it is produced
under conditions of stress and causes partial
closure of stomata under drought and thus acts
as antitranspirants.
19. (d)
Ethylene promotes abscission and senescence of
leaves, flowers etc.
20. (a)
Both statements are correct.
21. (b)
Ethephon is the compound used to supply
ethylene. It is readily absorbed in aqueous solution
and transported within the plant and it releases
ethylene slowly. Ethephon hastens fruit ripening
in tomatoes and apples. It accelerates abscission
of flowers and fruits in cotton, cherry, walnut,
etc.
22. (d)
Abscissic acid (ABA), also known as abscisin II
and dormin. It is usually found in vascular plants,
some fungi and some green algae. It acts as an
inhibitor because it opposes the growth of
promoting effect of auxins, GA and cytokinins,
thus keep their activity under control. Leaf
abscission, fruit fall and dormancy occurs due to
abscissic acid.
23. (b)
In guard cells, the plant hormone abscisic acid
(ABA) inhibits stomatal opening and induces
stomatal closure through the coordinated
regulation of ion transport.
24. (a)
ABA counteracts many effects of GA such as
induction of hydrolases and ?-amylase in barley
seedlings.
25. (c)
(v) The cells in meristematic phase region are
rich in protoplasm, possess large conspicuous
nuclei and cell walls are primary in nature.
(vi) Increased vacuolation, cell enlargement and
new cell wall deposition are the characteristics
of the cells in phase of elongation region.
26. (a)
(i) On plotting the length of the organ against
time, a linear curve is obtained.
(ii) Mathematically, it is expressed as L
t 
= L
0
 + rt.
Both these statements are correct
regarding arithmetic growth.
27. (d)
All statements are correct.
28. (b)
(iv) Skoog and Miller identified and crystallised
the cytokinesis promoting active substance
that they termed kinetin.
(v) Inhibitor-B, abscission II and dormin were
chemically identical and named as abscisic
acid (ABA).
29. (d)
All the given statements are the characteristics
of growth of an organism. Growth can be
defined as an irreversible permanent increase
in size of an organ or its parts or even of an
individual cell.
30. (d)
Water does not oxidize glucose to provide energy.
It maintains the turgidity of growing cells and
provides medium for enzymatic reactions.
31. (a)
IAA and IBM are natural auxins but NAA, 2, 4 -
D and 2, 4, 5 T are synthetic auxins.
32. (c)
Ethylene promotes senescence and abscission of
plant organs especially of leaves and flowers. It
enhances the respiration rate during fruit ripening.
Ethylene is also used to initiate flowering and for
synchronising fruit-set in pineapples. It also
induces flowering in mango.
33. (d)
All the given statements regarding ethephon are
correct. Ethephon is a synthetic plant growth
regulator that induces flowering and abscission
by promoting the release of ethylene and has been
used to cause early ripening (as of apples on the
tree).
34. (b)
Gibberellin helps in cell growth of stem, leaves
and other aerial parts.
35. (c)
The plant growth regulators (PGRs) are small,
simple molecule of diverse chemical composition.
They could be indole compounds (indole-3-acetic
acid, (IAA, IBA); adenine derivatives (N
6
-
furfurylamino purine, kinetin) derivatives of
carotenoids (abscisic acid); terpenes (gibberellic
acid, GA
3
) or gases (ethylene, C
2
H
4
).
36. (b)
(II) The cells proximal to the meristematic zone
represent the phase of elongation.
37. (a)
Both statements are correct.
38. (b)
(II) This act leading to maturation is termed as
differentiation.
39. (b)
IBA (indole butyric acid) is a natural plant hormone
in the auxin family and is an ingredient in many
commercial horticultural plant rooting products. It is
used for stimulating plant growth and root formation.
40. (c)
(I) Difference in shapes of leaves produced in
air and those produced in water in buttercup.
41. (c)
Flowering in pineapple is promoted by NAA
(Naphthalene acetic acid). NAA is a synthetic
plant hormone in the auxin family. NAA and 2, 4,
D are synthetic auxin plant hormones. All these
auxins have been used extensively in agricultural
and horticultural practices.
42. (a)
Indole compounds (e.g, IAA, IBA) help to prevent
fruit and leaf drop at early stage but promote the
abscission of older mature leaves and fruits. Indole
is an aromatic heterocyclic organic compound. It
has a bicyclic structure, consisting of a six-
membered benzene ring fused to a five-membered
nitrogencontaining pyrrole ring.
43. (b)
(II) ABA stimulates the closure of stomata and
increases the tolerance of plants to various
kinds of stresses.
44. (b)
(i) Spraying juvenile conifers with Gibberellins
hastens the maturity period, thus leading to
early seed production.
(ii) Gibberellins promotes bolting in beet,
cabbages and many plants with rosette habit.
(iii) Cytokinins helps to produce new leaves,
chloroplasts in leaves, lateral shoot growth
and adventitious shoot formation.
(iv) The ability of Gibberellins to cause an
increase in length of axis is used to increase
the length of grapes stalks.
45. (d)
All statements are correct.
46. (c)
Growth is defined as a permanent or irreversible
increase in the dry weight, size, mass or volume
of a cell, organ or organism. Generally, growth is
accompanied by metabolic processes (both
anabolic and catabolic), that occur at the expense
of energy.
47. (c)
Reason : Plants have hormones called
phytohormones. These can increase the reaction
rate and can also decrease the rate of reaction.
They can either promote growth or be inhibitory
in action.
48. (a)
Plant growth is unique because plants retain the
capacity for unlimited growth throughout their life.
This ability of the plants is due to the presence of
meristems at certain locations in their body. The
cells of such meristems have the capacity to divide
and self-perpetuate. The product, however, soon
loses the capacity to divide and such cells make
up the plant body. This form of growth wherein
new cells are always being added to the plant body
by the activity of the meristem is called the open
form of growth.
49. (a)
Arithmetic growth is a type of growth in which
the rate of growth is constant and increase in
growth occurs in arithmetic progression i.e., 2, 4,
6, 8 etc. Here after mitosis, only one daughter
cell continues to divide and other takes part in
differentiation and maturation. Here a linear curve
is obtained with positive value.
50. (a)
The rate of growth can be measured by an
increase in size or area of an organ of the plant
like leaf, flower, fruit etc. in a unit time. The rate
of growth is also called efficiency index.
51. (c)
Differentiation is maturation of cells derived from
optical meristems of root and shoot. It is applied
to the qualitative differences between cells, tissues
and organs. During differentiation cell undergoes
few to major anatomical and physiological
changes both in their cell walls and protoplasm.
For example, to form tracheary element, the cells
would lose their protoplasm.
52. (c)
In different phases of growth, plants follow
different pathways and form different kinds of
structures in response to environment. The ability
to change under the influence of internal or
external stimuli is called plasticity, e.g.,
heterophylly in cotton, coriander and larkspur.
Occurence of different types of structures on
same plant in different growth phases or under
different environment conditions is known as
heterophylly.
53. (c)
During mid- 1960s, three independent researches
reported the purification and chemical
characterization of three different kinds of
inhibiters : inhibitor - B, abscission II and dormin.
Later all the three were proven to be chemically
identical. It was named abscisic acid (ABA).
ABA plays an important role in seed development,
maturation & dormancy.
54. (a)
Auxin is a weakly acidic hormone having an
unsaturated ring structure and promotes cell
elongation especially in shoots. Auxins was first
isolated from human urine. Auxins like IAA and
IBA have been isolated from plants. NAA and 2,
4 - D are synthetic auxins.
55. (d)
Auxins inhibit the growth of axillary buds and
promote apical dominance. It induces
parthenocarpic development of fruits and such
fruits are seedless and auxin is also responsible
for phototropism and geotropisms. Ripening and
maturity of fruits are related to ethylene.
56. (c)
(iii) Cytokinins helps to produce new leaves,
chloroplasts in leaves, lateral shoot growth
and adventitious shoot formation.
(v) Auxin help to initiate rooting in stem cuttings.
(vi) Auxins promote flowering e.g. in pineapples.
57. (c)
(i) Cytokinins have specific effects on
cytokinesis.
(ii) Cytokinins is a modified form of adenine.
(iii) Kinetin does not occur naturally in plants.
(iv) Zeatin is isolation from coconut milk.
58. (b)
(i) Ethylene is a simple gaseous PGR.
(ii) Ethylene is synthesised in large amounts by
tissues undergoing senescence and ripening fruits.
(iii) Influences of  ethylene on plants include
horizontal growth of seedlings, swelling of the
axis and apical hook formation in dicot seedlings.
(iv) Ethylene promotes senescence and abscission
of plant organs especially of leaves and flowers.
59. (d)
All statements are correct.
60. (d)
Heterophylly is referred to the development of
different leaf forms in a single plant depending
on the condition of environment.
In buttercup, leaves in water and air have
different shape.
61. (b)
The growth of the leaf is measured in terms of
surface area.
62. (c)
Reason : Maize root apical meristem produces
17,500 new cells in one hour and the growth is
due to increase in number.
63. (a)
A : Abscissic acid (ABA), also known as
abscisin II and dormin. It is usually found in
vascular plants, some fungi and some green
algae. It was discovered for its role in
regulating abscission and dormancy. It
simulates the closure of stomata in the
epidermis and increases the tolerance of
plants to various kinds of stresses, therefore
it is also called as stress hormone.
B : Ethylene is a gaseous plant hormone.
C : Cytokinins are found in abundance in young
roots, leaves and young fruits where rapid
cell division occurs and are synthesized in the
meristematic regions of the plants. They are
responsible for mitosis, chloroplast
development, and differentiation of the shoot
meristem, stimulating the development of
lateral buds and therefore branching,
differentiation of the tissues of the root, leaf
formation and leaf senescence.
D : Auxin is a plant hormone which causes the
elongation of cells in shoots and is involved
in regulating plant growth. They are also
responsible for apical dominance.
64. (a)
In arithmetic growth, following mitotic cell division,
only one daughter cell continues to divide while
the other differentiates and matures. The simplest
example of arithmetic growth is explained by a
root elongating at a constant rate.
When the length of the organ is plotted against
time, a linear curve is obtained.
65. (a)
In geometrical growth, both the progeny cells
following mitotic cell division retain the ability to
divide and continue to do so. However, with a
limited supply of nutrients, the growth becomes
slow which leads to the stationary stage. A sigmoid
curve is the characteristic of organisms living in
the natural environment.
66. (a)
Water is vital and required for various purposes in
plants. For example, during cell elongation and for
maintenance of turgidity of growing cells, water is
crucial. Water also provides a medium for enzyme
action inside plant cells, helps in the uptake of
nutrients from soil and maintains the osmolarity of
cells. Even the slightest of deficiency of water in
plants can cause reduced growth due to reduced
photosynthetic yield. Water stress completely stops
growth.
67. (d)
Coconut milk factor is a cytokinin. Kinetin does
not occur naturally in plants. Search for natural
substances with cytokinin-like activities led to the
isolation of zeatin from corn-kernels and coconut
milk.
68. (b)
The option (b) shows the correct graph of
arithmetic growth. Arithmetic growth refers to
the situation where a population increases by a
constant number of persons (or other objects) in
each period being analysed. In arithmetic growth,
following mitotic cell division, only one daughter
cell continues to divide while the other
differentiates and matures. On plotting length of
the organ against time, a linear curve is obtained.
69. (d)
The constantly dividing cells, both at the root apex
and the shoot apex, represent the meristematic phase
of growth. The cells in this region are rich in
protoplasm, possess large conspicuous nuclei. Their
cell walls are primary in nature, thin and cellulosic
with abundant plasmodesmatal connections.