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NCERT Solutions for Class 11th BIOLOGY
Chapter 5 Morphology of Flowering Plants
Question 1: What is meant by modification of root? What type of modification of root is found in the
(a) Banyan tree
(b) Turnip
(c) Mangrove trees
Answer Primarily, there are two types of root systems found in plants, namely the tap root system and fibrous root system. e main function of the roots is to absorb water and minerals from the soil. However, roots are also modified to perform various other functions. The roots of some plants act as storage sites for food, some provide support to massive plant structures, while others absorb oxygen from the atmosphere.
Roots and its modifications in various plants:
(a) Banyan tree
The banyan tree (Ficus benghalensis) has massive pillar-like adventitious roots arising from the aerial part of the stem. These roots grow towards the ground and provide support to the tree. Such roots are called prop roots.
(b) Turnip
The roots of turnip (Brassica rape) help in the storage of food. Similar food-storing roots are found in radishes, carrots, and sweet potatoes.
(c) Mangrove tree
The roots of mangrove plants grow vertically upwards from the soil for the absorption of oxygen from the atmosphere as the soil is poorly aerated. These types of roots are called pneumatophores.
(a) Banyan tree
(b) Turnip
(c) Mangrove trees
Answer Primarily, there are two types of root systems found in plants, namely the tap root system and fibrous root system. e main function of the roots is to absorb water and minerals from the soil. However, roots are also modified to perform various other functions. The roots of some plants act as storage sites for food, some provide support to massive plant structures, while others absorb oxygen from the atmosphere.
Roots and its modifications in various plants:
(a) Banyan tree
The banyan tree (Ficus benghalensis) has massive pillar-like adventitious roots arising from the aerial part of the stem. These roots grow towards the ground and provide support to the tree. Such roots are called prop roots.
(b) Turnip
The roots of turnip (Brassica rape) help in the storage of food. Similar food-storing roots are found in radishes, carrots, and sweet potatoes.
(c) Mangrove tree
The roots of mangrove plants grow vertically upwards from the soil for the absorption of oxygen from the atmosphere as the soil is poorly aerated. These types of roots are called pneumatophores.
2.Justify the following statements on the basis of external features:
(i) Underground parts of a plant are not always roots.
(ii) Flower is a modified shoot.
Soln. (i) Underground parts of plant are not always roots because sometimes the stem also becomes underground and gets modified into various forms to perform different functions of storage, vegetative propagation, perennation, etc. Underground modifications of stems are tuber, rhizome, corm and bulb. The underground stems can be distinguished from roots externally by the presence of nodes and internodes, axillary buds, scale leaves etc. and by absence of root cap and root hairs.
(ii) Flower is the reproductive part of the angiospermic plant and it is defined as the modified shoot because (a) like shoot, flower develops from an axillary or rarely terminal bud. (b) flowers may get modified into fleshy buds or bulbils, (c) A transition from foliage leaves to floral leaves is found in Paeonia. (d) Nymphaea shows transition from sepals to petals and petals to stamens, (e) In Passiflora and Cleome long intemodes occur below gynoecium and stamens.
(i) Underground parts of a plant are not always roots.
(ii) Flower is a modified shoot.
Soln. (i) Underground parts of plant are not always roots because sometimes the stem also becomes underground and gets modified into various forms to perform different functions of storage, vegetative propagation, perennation, etc. Underground modifications of stems are tuber, rhizome, corm and bulb. The underground stems can be distinguished from roots externally by the presence of nodes and internodes, axillary buds, scale leaves etc. and by absence of root cap and root hairs.
(ii) Flower is the reproductive part of the angiospermic plant and it is defined as the modified shoot because (a) like shoot, flower develops from an axillary or rarely terminal bud. (b) flowers may get modified into fleshy buds or bulbils, (c) A transition from foliage leaves to floral leaves is found in Paeonia. (d) Nymphaea shows transition from sepals to petals and petals to stamens, (e) In Passiflora and Cleome long intemodes occur below gynoecium and stamens.
Question 3: How is pinnately compound leaf different from palmately compound leaf?Answer
4.Explain with suitable examples the different types of phyllotaxy.
Soln.Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. It is usually of three types – alternate, opposite and whorled. In alternate type of phyllotaxy, a single leaf arises at each node in alternate manner, as in china rose, mustard and sunflower plants. In opposite type, a pair of leaves arises at each node and lie opposite to each other as in Calotropis and guava plants.
If more than two leaves arise at a node and form a whorl it is called whorled phyllotaxy as in Alstonia.
Soln.Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. It is usually of three types – alternate, opposite and whorled. In alternate type of phyllotaxy, a single leaf arises at each node in alternate manner, as in china rose, mustard and sunflower plants. In opposite type, a pair of leaves arises at each node and lie opposite to each other as in Calotropis and guava plants.
If more than two leaves arise at a node and form a whorl it is called whorled phyllotaxy as in Alstonia.
Question 5: Define the following terms:
(a) Aestivation
(b) Placentation
(c) Actinomorphic DOWNLOAD THE FULL APP
(d) Zygomorphic
(e) Superior ovary
(f) Perigynous flower
(g) Epipetalous Stamen
Answer (a) Aestivation
The term ‘aestivation’ refers to the mode in which sepals or petals are arranged in a floral bud with respect to other floral members. There are four types of aestivation in plants i.e., valvate, twisted, imbricate, and vexillary.
(b) Placentation
The term ‘placentation’ refers to the arrangement of ovules within the ovary of a flower. It is primarily of five types, namely marginal, basal, parietal, axile, and free central.
(c) Actinomorphic
Actinomorphic flowers can be divided into two radial halves by any radial plane passing through its centre. Examples of these flowers include chilly and mustard.
(d)Zygomorphic
Zygomorphic flowers are those flowers which can be divided into two similar halves by a single vertical plane. Examples of these flowers include pea and beans.
(e) Superior ovary
Superior ovary flowers are those flowers in which the gynoecium is present at the highest position, while other floral parts are arranged below it. A flower with this arrangement is described as hypogynous. Examples include brinjal and mustard.
(f) Perigynous flower
In perigynous flowers, the gynoecium is present in the centre and the rest of the floral parts are arranged at the rim of the thalamus at the same level. Examples include plum and rose.
(g) Epipetalous Stamen
Epipetalous stamens are stamens attached to the petals. They are found in brinjal.
(a) Aestivation
(b) Placentation
(c) Actinomorphic DOWNLOAD THE FULL APP
(d) Zygomorphic
(e) Superior ovary
(f) Perigynous flower
(g) Epipetalous Stamen
Answer (a) Aestivation
The term ‘aestivation’ refers to the mode in which sepals or petals are arranged in a floral bud with respect to other floral members. There are four types of aestivation in plants i.e., valvate, twisted, imbricate, and vexillary.
(b) Placentation
The term ‘placentation’ refers to the arrangement of ovules within the ovary of a flower. It is primarily of five types, namely marginal, basal, parietal, axile, and free central.
(c) Actinomorphic
Actinomorphic flowers can be divided into two radial halves by any radial plane passing through its centre. Examples of these flowers include chilly and mustard.
(d)Zygomorphic
Zygomorphic flowers are those flowers which can be divided into two similar halves by a single vertical plane. Examples of these flowers include pea and beans.
(e) Superior ovary
Superior ovary flowers are those flowers in which the gynoecium is present at the highest position, while other floral parts are arranged below it. A flower with this arrangement is described as hypogynous. Examples include brinjal and mustard.
(f) Perigynous flower
In perigynous flowers, the gynoecium is present in the centre and the rest of the floral parts are arranged at the rim of the thalamus at the same level. Examples include plum and rose.
(g) Epipetalous Stamen
Epipetalous stamens are stamens attached to the petals. They are found in brinjal.
6.Differentiate between
(a) Racemose and cymose inflorescence
(b) Fibrous root and adventitious root
(c) Apocarpous and syncarpous ovary
Soln.
(a) Differences between racemose and cymose inflorescence are as follows:
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(b) Differences between fibrous and adventitious roots are as follows :
(c) Differences between apocarpous and syncarpous ovary are as follows :
(a) Racemose and cymose inflorescence
(b) Fibrous root and adventitious root
(c) Apocarpous and syncarpous ovary
Soln.
(a) Differences between racemose and cymose inflorescence are as follows:
DOWNLOAD THE FULL APP(b) Differences between fibrous and adventitious roots are as follows :
(c) Differences between apocarpous and syncarpous ovary are as follows :
Question 7:Draw the labelled diagram of the following:
(i) Gram seed
(ii) V.S. of maize seed
Answer
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(i) Gram seed
(ii) V.S. of maize seed
Answer
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8.Describe modifications of stem with suitable examples.
Soln. Stems are modified to perform different functions. Underground stems of some plants are modified to store food in them. They also act as organs of perennation to tide over conditions unfavourable for growth. Different modifications of stem are :
(i) Underground modifications
(ii)Sub-aerial modifications
(iii)Aerial modifications
(i)Underground modifications of stem are discussed as follows:
(a)Tuber: It is the branch of main stem which accumulates or stores food in it and swells up, e.g., Solarium tuberosum (potato).
(b) Rhizome: It is a branched, prostrate horizontally growing stem having nodes and internodes. On the nodes sessile scale leaves are formed, e.g., Carina, Zingiber officinale (ginger), Curcuma domestica (turmeric) etc.
(c) Corm: This is a spherical,
branched, vertically growing thick underground stem with more diameter than length, e.g., Crocus sativus (saffron), Gladiolus, Colocasia esculenta (arvi) etc.
(d) Bulb: In bulb the stem is highly reduced and can be seen only as a disc-like structure bearing numerous fleshy scaly leaves, e.g., Allium cepa (onion), Allium sativum (garlic) etc.
(ii) Subaerial modifications : Subaerial part of stem grows horizontally on the ground while some part remains underground. Vegetative propagation takes place by means of these. They may be of following kinds.
(a) Runner: It grows prostrate on the surface of soil. It develops at the base of erect shoot called crown. A number of runners arise from one erect shoot which spread in different directions. Each runner has one or more nodes which bear scale leaves and axillary buds, e.g., Cynodon (doob grass).
(b) Stolon: The nodes of horizontally growing underground stem give rise to branches which come out of the soil, e.g., Fragaria (strawberry).
(c) Sucker: Suckers are formed from the node of underground stem. Sucker comes up obliquely in the form of leafy shoot, e.g., Mentha (mint).
(d) Offset: Stem consists of thick and short intemodes. The branches are formed from the main stem and upper portion of each branch bears a group of leaves while the lower portion bears the roots. Each branch is capable of growing as an independent plant after separating from the parent plant, e.g., Eichhornia (water hyacinth), Pistia, etc.
(iii)Aerial modifications : The aerial portion of stem is modified to perform different functions, e.g., climbing, protection, food manufacturing, etc. It may show following types of modifications:
(a) Twinners : The stem is long, flexible and sensitive which can coil around an upright support like a rope, e.g., Ipomoea, Convolvulus.
(b) Climbers : The stem is weak and flexible but is unable to coil around an upright support by itself. It requires the help of clasping or clinging structures. Accordingly, climbers are of four types : root climbers, e.g., Betel; tendril climber, e.g., Passiflora; scramblers, e.g., Bougainvillea and lianas, e.g., Bauhinia.
(c) Phylloclade: The stem performs the function of photosynthesis. The stem modifies into green fleshy leaf-like
structure having distinct nodes and intemodes. Leaves of such plants are reduced into spines in order to prevent loss of water, e.g., Opantia (prickly pear), Euphorbia.
(d) Cladode: It is similar to phylloclade with only one internode, e.g., Asparagus.
(e) Thorn: Stem is modified into stiff, pointed unbranched or branched structures which have lost their growing point and become hard, called as thorns, e.g., Bougainvillea,Pomegranate, Citrus, etc. They perform defensive function.
(f) Tendrils : These are thread like sensitive structures which can coil around a support and help the plant
in climbing, e.g., Cucurbita.
(g) Bulbils: In some plants vegetative buds or floral buds modify into a swollen structure called bulbil. It separates from the parent plant and on approach of favourable condition gives rise to a new plant, i.e., it is an organ of vegetative reproduction, e.g., Agave, Oxalis.\
Soln. Stems are modified to perform different functions. Underground stems of some plants are modified to store food in them. They also act as organs of perennation to tide over conditions unfavourable for growth. Different modifications of stem are :
(i) Underground modifications
(ii)Sub-aerial modifications
(iii)Aerial modifications
(i)Underground modifications of stem are discussed as follows:
(a)Tuber: It is the branch of main stem which accumulates or stores food in it and swells up, e.g., Solarium tuberosum (potato).
(b) Rhizome: It is a branched, prostrate horizontally growing stem having nodes and internodes. On the nodes sessile scale leaves are formed, e.g., Carina, Zingiber officinale (ginger), Curcuma domestica (turmeric) etc.
(c) Corm: This is a spherical,
branched, vertically growing thick underground stem with more diameter than length, e.g., Crocus sativus (saffron), Gladiolus, Colocasia esculenta (arvi) etc.
(d) Bulb: In bulb the stem is highly reduced and can be seen only as a disc-like structure bearing numerous fleshy scaly leaves, e.g., Allium cepa (onion), Allium sativum (garlic) etc.
(ii) Subaerial modifications : Subaerial part of stem grows horizontally on the ground while some part remains underground. Vegetative propagation takes place by means of these. They may be of following kinds.
(a) Runner: It grows prostrate on the surface of soil. It develops at the base of erect shoot called crown. A number of runners arise from one erect shoot which spread in different directions. Each runner has one or more nodes which bear scale leaves and axillary buds, e.g., Cynodon (doob grass).
(b) Stolon: The nodes of horizontally growing underground stem give rise to branches which come out of the soil, e.g., Fragaria (strawberry).
(c) Sucker: Suckers are formed from the node of underground stem. Sucker comes up obliquely in the form of leafy shoot, e.g., Mentha (mint).
(d) Offset: Stem consists of thick and short intemodes. The branches are formed from the main stem and upper portion of each branch bears a group of leaves while the lower portion bears the roots. Each branch is capable of growing as an independent plant after separating from the parent plant, e.g., Eichhornia (water hyacinth), Pistia, etc.
(iii)Aerial modifications : The aerial portion of stem is modified to perform different functions, e.g., climbing, protection, food manufacturing, etc. It may show following types of modifications:
(a) Twinners : The stem is long, flexible and sensitive which can coil around an upright support like a rope, e.g., Ipomoea, Convolvulus.
(b) Climbers : The stem is weak and flexible but is unable to coil around an upright support by itself. It requires the help of clasping or clinging structures. Accordingly, climbers are of four types : root climbers, e.g., Betel; tendril climber, e.g., Passiflora; scramblers, e.g., Bougainvillea and lianas, e.g., Bauhinia.
(c) Phylloclade: The stem performs the function of photosynthesis. The stem modifies into green fleshy leaf-like
structure having distinct nodes and intemodes. Leaves of such plants are reduced into spines in order to prevent loss of water, e.g., Opantia (prickly pear), Euphorbia.
(d) Cladode: It is similar to phylloclade with only one internode, e.g., Asparagus.
(e) Thorn: Stem is modified into stiff, pointed unbranched or branched structures which have lost their growing point and become hard, called as thorns, e.g., Bougainvillea,Pomegranate, Citrus, etc. They perform defensive function.
(f) Tendrils : These are thread like sensitive structures which can coil around a support and help the plant
in climbing, e.g., Cucurbita.
(g) Bulbils: In some plants vegetative buds or floral buds modify into a swollen structure called bulbil. It separates from the parent plant and on approach of favourable condition gives rise to a new plant, i.e., it is an organ of vegetative reproduction, e.g., Agave, Oxalis.\
Question 9: Take one flower each of families Fabaceae and Solanaceae and write its semi-technical description. Also draw their floral diagrams after studying them.
Answer (1) Family Fabaceae/Papilionaceae (pea plant)
Fabaceae/Papilionaceae is a sub-family of the Leguminoseae family.
Vegetative features:
Habit: Pinnately compound, alternately arranged with leaf tendrils with the pulvinus present at the leaf base along folacious stipules.
Root: Tap root system with root nodules.
Floral features:
Inflorescence: Racemose, generally axial than terminal Flower: Zygomorphic and bisexual flowers are found
Calyx: It contains five sepals which are gamosepalous while aestivation is imbricate. Corolla: It contains five petals (polypetalous) with vexillary aestivation. Androecium: It consists of ten anthers that are diadelphous with dithecous anthers. Gynoecium: Monocarpellary superior ovary which is unilocular with marginal placentation.
Fruit: Legume pod with non-endospermic seeds
Floral formula:
Economic importance: Peas are used as vegetables for making various culinary preparations.
(2) Flowers of Solanum nigrum
Family Solanaceae
Vegetative features:
Habit: Erect, herbaceous plant
Leaves: Simple, exstipulate leaves with reticulate venation Stem: Erect stem with numerous branches.
Floral features:
Inflorescence: Solitary and axillary Flowers: Actinomorphic, bisexual flowers
Calyx: Calyx is composed of five sepals that are united and persistent. Aestivation is valvate.
Corolla: Corolla consists of five united petals with valvate aestivation. Androecium: It consists of five epipetalous stamens.
Gynoecium: It consists of bicarpellary syncarpous superior ovary with axile placentation.
Fruits: Berry
Seeds: Numerous, endospermous
Floral formula:
Economic importance: Peas are used as vegetables for making various culinary preparations.
Answer (1) Family Fabaceae/Papilionaceae (pea plant)
Fabaceae/Papilionaceae is a sub-family of the Leguminoseae family.
Vegetative features:
Habit: Pinnately compound, alternately arranged with leaf tendrils with the pulvinus present at the leaf base along folacious stipules.
Root: Tap root system with root nodules.
Floral features:
Inflorescence: Racemose, generally axial than terminal Flower: Zygomorphic and bisexual flowers are found
Calyx: It contains five sepals which are gamosepalous while aestivation is imbricate. Corolla: It contains five petals (polypetalous) with vexillary aestivation. Androecium: It consists of ten anthers that are diadelphous with dithecous anthers. Gynoecium: Monocarpellary superior ovary which is unilocular with marginal placentation.
Fruit: Legume pod with non-endospermic seeds
Floral formula:
Economic importance: Peas are used as vegetables for making various culinary preparations.
(2) Flowers of Solanum nigrum
Family Solanaceae
Vegetative features:
Habit: Erect, herbaceous plant
Leaves: Simple, exstipulate leaves with reticulate venation Stem: Erect stem with numerous branches.
Floral features:
Inflorescence: Solitary and axillary Flowers: Actinomorphic, bisexual flowers
Calyx: Calyx is composed of five sepals that are united and persistent. Aestivation is valvate.
Corolla: Corolla consists of five united petals with valvate aestivation. Androecium: It consists of five epipetalous stamens.
Gynoecium: It consists of bicarpellary syncarpous superior ovary with axile placentation.
Fruits: Berry
Seeds: Numerous, endospermous
Floral formula:
Economic importance: Peas are used as vegetables for making various culinary preparations.
10.Describe the various types of placentations found in flowering plants.
Soln.Placenta is a parenchymatous cushion present inside the ovary where ovules are borne. The number, position, arrangement or distribution of placentae inside an ovary is called placentation. The placentation are of different types namely, marginal, axile, parietal, basal and free central.
(i)Marginal placentation : The placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows, e.g., pea.
(ii)Axile placentation : When the placenta is axial and the ovules are attached to it in a multilocular ovary, the placentation is said to be axile, e.g., china rose, tomato and lemon.
(iii)Parietal placentation : The ovules develop on the inner wall of the ovary or on peripheral part. Ovary is one-chambered but it becomes two-chambered due to the formation of the false septum, e.g., mustard and Argemone.
(iv)Free central placentation : When the ovules are borne on central axis and septa are absent, as in Dianthus and primrose the placentation is called free central.
(v)Basal placentation: The placenta develops at the base of ovary and a single ovule is attached to it, as in sunflower, marigold.
Soln.Placenta is a parenchymatous cushion present inside the ovary where ovules are borne. The number, position, arrangement or distribution of placentae inside an ovary is called placentation. The placentation are of different types namely, marginal, axile, parietal, basal and free central.
(i)Marginal placentation : The placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows, e.g., pea.
(ii)Axile placentation : When the placenta is axial and the ovules are attached to it in a multilocular ovary, the placentation is said to be axile, e.g., china rose, tomato and lemon.
(iii)Parietal placentation : The ovules develop on the inner wall of the ovary or on peripheral part. Ovary is one-chambered but it becomes two-chambered due to the formation of the false septum, e.g., mustard and Argemone.
(iv)Free central placentation : When the ovules are borne on central axis and septa are absent, as in Dianthus and primrose the placentation is called free central.
(v)Basal placentation: The placenta develops at the base of ovary and a single ovule is attached to it, as in sunflower, marigold.
Question 11: What is a flower? Describe the parts of a typical angiosperm flower?
Answer A flower can be defined as the reproductive unit of any flowering plant (angiosperms). Flowers carry out sexual reproduction in angiosperms. A typical flower is a modified stem with a condensed axis. A flower has four different parts i.e., the calyx, corolla, androecium, and gynoecium. Androecium and gynoecium represent the male and female reproductive organs of a flower (respectively). Bisexual flowers are those which contain both androecium and gynoecium, while unisexual flowers contain either gynoecium or androecium. The corolla and the calyx are generally distinct, but may sometimes be fused (called perianth). A flower that contains all four floral parts is called a complete flower.
Parts of flowers
(A) The calyx forms the outermost whorl of a flower, which contains sepals. They are green, leaf–like structures that cover and protect the flowers during the bud stage. When the sepals of a flower are free, they are called polysepalous, while fused sepals of a flower are called gamosepalous.
(B) The corolla of a flower is a layer that lies inside the calyx. It contains beautifully coloured petals, which help in attracting insects for pollination. When the petals are free, they are called polypetalous, while fused petals are called gamopetalous.
(C) The androecium or the stamen is the male reproductive part of a flower. It consists of two parts, the filament and the bilobed anther. The bilobed anther is the site for meiosis and the generation of pollen grains.
(D) Gynoecium represents the female reproductive part of a flower. It consists of an ovary. The ovary is connected by a long tube (called style) to the stigma. The ovary bears numerous ovules attached to the placenta.
Answer A flower can be defined as the reproductive unit of any flowering plant (angiosperms). Flowers carry out sexual reproduction in angiosperms. A typical flower is a modified stem with a condensed axis. A flower has four different parts i.e., the calyx, corolla, androecium, and gynoecium. Androecium and gynoecium represent the male and female reproductive organs of a flower (respectively). Bisexual flowers are those which contain both androecium and gynoecium, while unisexual flowers contain either gynoecium or androecium. The corolla and the calyx are generally distinct, but may sometimes be fused (called perianth). A flower that contains all four floral parts is called a complete flower.
Parts of flowers
(A) The calyx forms the outermost whorl of a flower, which contains sepals. They are green, leaf–like structures that cover and protect the flowers during the bud stage. When the sepals of a flower are free, they are called polysepalous, while fused sepals of a flower are called gamosepalous.
(B) The corolla of a flower is a layer that lies inside the calyx. It contains beautifully coloured petals, which help in attracting insects for pollination. When the petals are free, they are called polypetalous, while fused petals are called gamopetalous.
(C) The androecium or the stamen is the male reproductive part of a flower. It consists of two parts, the filament and the bilobed anther. The bilobed anther is the site for meiosis and the generation of pollen grains.
(D) Gynoecium represents the female reproductive part of a flower. It consists of an ovary. The ovary is connected by a long tube (called style) to the stigma. The ovary bears numerous ovules attached to the placenta.
12. How do the various leaf modifications help plants?
Soln.Leaves perform various functions besides photosynthesis and thus they are modified into different forms such as –
(i)Leaf tendrils: The different parts of a leaf are modified into tendrils which help the plant in climbing up. Parts of leaf modified into tendrils include stipules e.g., Smiiax ; petiole e.g., Clematis ; leaf apex e.g., Gloriosa ; leaflets e.g., Pisum; whole leaf e.g., Lathyrus.
(ii)Leaf spines: Either for the protection of plant or to lessen the rate of transpiration in xerophytic plants, the leaves modify into sharp, pointed spines. Parts of leaf modified into leaf spines include stipules e.g., Zizyphus; leaf margins e.g., Argemone; leaf apex e.g.r Yucca; entire leaf e.g., Berberis.
(iii)Phyllode: Petioles modify into leaf¬like green, photosynthesising structure e.g., Parkinsonia, Acacia auriculiformis.
(iv)Scale or protective leaves : The leaves modify into hard scaly leaves which protect the vegetative bud by covering them, e.g., Ficus, Artocarpus, Casuarina, etc.
(v) Leaf hooks : They help in climbing e.g., Bignonia.
(vi)Leaf roots : A leaf transforms into roots for balancing on water e.g., Salvinia.
(vii)Leaf pitchers : Leaf is modified into pitcher e.g., Nepenthes (insectivorous), Dischidia (non-insectivorous).
(viii)Leaf bladder: The leaves modify to form bladder like structure which trap insects and then it is closed by a valve present on the mouth of bladder e.g., Utricularia (bladderwort).
(ix) Leaf tentacles: The leaf of sundew plant, Drosera bear minute hairs which have shinning, sticky substance at their tips (tentacles). When any insect sits on the leaf, it is covered by these hairs.
Soln.Leaves perform various functions besides photosynthesis and thus they are modified into different forms such as –
(i)Leaf tendrils: The different parts of a leaf are modified into tendrils which help the plant in climbing up. Parts of leaf modified into tendrils include stipules e.g., Smiiax ; petiole e.g., Clematis ; leaf apex e.g., Gloriosa ; leaflets e.g., Pisum; whole leaf e.g., Lathyrus.
(ii)Leaf spines: Either for the protection of plant or to lessen the rate of transpiration in xerophytic plants, the leaves modify into sharp, pointed spines. Parts of leaf modified into leaf spines include stipules e.g., Zizyphus; leaf margins e.g., Argemone; leaf apex e.g.r Yucca; entire leaf e.g., Berberis.
(iii)Phyllode: Petioles modify into leaf¬like green, photosynthesising structure e.g., Parkinsonia, Acacia auriculiformis.
(iv)Scale or protective leaves : The leaves modify into hard scaly leaves which protect the vegetative bud by covering them, e.g., Ficus, Artocarpus, Casuarina, etc.
(v) Leaf hooks : They help in climbing e.g., Bignonia.
(vi)Leaf roots : A leaf transforms into roots for balancing on water e.g., Salvinia.
(vii)Leaf pitchers : Leaf is modified into pitcher e.g., Nepenthes (insectivorous), Dischidia (non-insectivorous).
(viii)Leaf bladder: The leaves modify to form bladder like structure which trap insects and then it is closed by a valve present on the mouth of bladder e.g., Utricularia (bladderwort).
(ix) Leaf tentacles: The leaf of sundew plant, Drosera bear minute hairs which have shinning, sticky substance at their tips (tentacles). When any insect sits on the leaf, it is covered by these hairs.
Question 13: Define the term inflorescence. Explain the basis for the different types of inflorescence in flowering plants.
Answer Inflorescence is the manner in which the flowers are arranged on the flowering axis. During the flowering season, the vegetative apex of the stem gets converted into a floral meristem. Based on whether the floral axis continues to grow or end in a flower, inflorescence is classified into racemose and cymose. In racemose inflorescence, the floral axis continues to grow and produces flowers laterally. On the other hand, in cymose inflorescence, the main axis terminates into a flower. Hence, it is limited in growth.
Answer Inflorescence is the manner in which the flowers are arranged on the flowering axis. During the flowering season, the vegetative apex of the stem gets converted into a floral meristem. Based on whether the floral axis continues to grow or end in a flower, inflorescence is classified into racemose and cymose. In racemose inflorescence, the floral axis continues to grow and produces flowers laterally. On the other hand, in cymose inflorescence, the main axis terminates into a flower. Hence, it is limited in growth.
14. Write the floral formula of an actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carples with superior ovary and axile placentation.
Soln. The floral formula for actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carples with superior ovary and
axile placentation is:
Soln. The floral formula for actinomorphic, bisexual, hypogynous flower with five united sepals, five free petals, five free stamens and two united carples with superior ovary and
axile placentation is:
15.Describe the arrangement of floral members in relation to their insertion on thalamus.
Soln. In a typical flower, the floral members like calyx, corolla, androecium and gynOecium are arranged over the thalamus! Based on the position of calyx, corolla and androecium in respect to ovary on thalamus, the flowers are described as hypogynous, perigynous and epigynous ones. In the hypogynous flower the gynoecium occupies the highest position while the other parts are situated below it. The ovary in such flowers is said to be superior, e.g., mustard, china rose and brinjal. If gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level, it is called perigynous. The ovary here is said to be half inferior or sub superior, e.g., plum, rose, peach. In epigynous flowers, the margin of thalamus grows upward enclosing the ovary completely and gets fused with it; the other parts of flower arise above the ovary. Hence, the ovary is said to be inferior as in flowers of guava and cucumber, and the ray florets of sunflower.
Soln. In a typical flower, the floral members like calyx, corolla, androecium and gynOecium are arranged over the thalamus! Based on the position of calyx, corolla and androecium in respect to ovary on thalamus, the flowers are described as hypogynous, perigynous and epigynous ones. In the hypogynous flower the gynoecium occupies the highest position while the other parts are situated below it. The ovary in such flowers is said to be superior, e.g., mustard, china rose and brinjal. If gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level, it is called perigynous. The ovary here is said to be half inferior or sub superior, e.g., plum, rose, peach. In epigynous flowers, the margin of thalamus grows upward enclosing the ovary completely and gets fused with it; the other parts of flower arise above the ovary. Hence, the ovary is said to be inferior as in flowers of guava and cucumber, and the ray florets of sunflower.
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