Inflorescence
Inflorescence is a cluster of flowers present on the same stalk called peduncle.
Depending upon the position on the stem, it could be terminal or axillary.
Types of inflorescence
The sexual reproduction in flowering plants is by the fusion of nuclei rather than cells and so the nuclei are termed as gametes.
Flower is a modified shoot with much condensed internodes and a number of appendages (floral leaves) at every node.
A flower is said to be a modified shoot for sexual reproduction.
Bract: a small leaf-like structure often positioned beneath a flower.
(i) Bracteate: a flower with a bract.
(ii) Ebracteate: a flower without bract.
Pedicel: the stalk of the flowers.
(i) Pedicellate: a flower with pedicel.
(ii) Sessile: a flower without pedicel.
Thalamus/Torus/Receptacle: the swollen end of the pedicel/axis, which bears floral leaves.
Complete flower: has all the four whorls.
Incomplete flower: one or more of the whorls is/are missing.
Bisexual/hermaphrodite flower: has both stamens and carpels.
Unisexual flower: has either stamens or carpels.
Staminate/male flower: only stamens are present.
Pistillate/female flower: only carpels are present.
Neuter flower: both stamens and carpels are absent.
Monoecious plant: bears both male and female flowers on the same pant. Ex: Maize, Castor bean
Dioecious plant: bears either male or female flowers. Ex: Papaya, Mulberry
Dichlamydeous flower: has both calyx and corolla
Monochlamydeous flower: has only one whorl; only corolla (asepalous) or only calyx(apetalous)
Actinomorphic/ radially symmetrical flower: flower can be cut into two identical halves, along any of the radii, passing through centre.
Zygomorphic: flower can be cut into two identical halves, only along one plane/radius, passing through centre. e.g. Pisum
Assymetrical: flower cannot be cut into two identical halves along any lane. e.g. Canna
Types of a Flower
Isomerous
It is the flower which has same number of floral leaves in each of the whorls.
(i) Dimerous: Floral leaves are in two's or multiples of it in each whorl.
(ii) Trimerous: Floral leaves are in threes or multiples of it in each whorl. e.g. flowers of monocots
(iii) Tetramerous: Floral leaves are in fours or multiples of it in each whorl. e.g. Brassicaceae
(iv) Pentamerous: Floral leaves are in fives or multiples of it in each whorl. e.g. most of the dicot flowers
Heteromerous
It is a flower which has different number of floral leaves in different whorls. e.g. member of Lamiaceae
Hypogynous
The ovary is situated on the trouts, above all other floral organs.
The ovary is superior.
Ex: Mustard, Tomato
Perigynous
The thalamus form a cup-like structure around the ovary and bears other floral organs almost at the same level on its rim.
The ovary is half superior or half inferior.
Ex: Rose, Pea
Epigynous
The thalamus form a cup which is fused with the ovary and all other floral organs arise on top of ovary.
The ovary is inferior.
Ex: Cucurbita, Sunflower
Parts of a Flower
A typical flower has four whorls namely,
(i) Calyx
(ii) Corolla
(iii) Androecium
(iv) Gynoecium/Pistil
Calyx
It is the first and the outermost whorl of a flower and it is composed of sepals.
It is generally green and leaf like and protects the flower bud before it opens.
The calyx may be polysepalous(sepals are free) or gamosepalous(sepals are fused together).
Corolla
It is the second whorl inner to sepals and is composed of petals.
It is generally large, brightly coloured and may have fragrance. They help in pollination by attracting insects.
The corolla may be polypetalous(petals are free from one another) or gamopetalous(petals are united together)
Perianth
The non-essential (non-reproductive) whorls of the flower constitute perianth.
The perianth is distinguished into an outer whorl of calyx and an inner whorl of corolla.
In other case, where perianth cannot be distinguished into calyx and corolla, the component segments are called tepals.
Aestivation
Aestivation refers to the arrangement of the segments of perianth in relation to one another in the bud condition.
Types of Aestivation
(i) Valvate: The margins of the sepals/petals/tepals just touch one another but there is no overlapping. e.g. Calatropis
(ii) Twisted/Contorted: One margin of each of the sepal/petals/tepals overlaps the margin of the next member. e.g. Hibiscus
(iii) Ascendingly Imbricate: One of the sepal/petal is completely internal with both the margins being overlapped and one of the sepals/petals is completely external and remaining are in twisted pattern. e.g. Mustard
(iv) Descendigly Imbricate/Vexillary/Papilionaceous: The posterior petal, vexillum is completely external and overlaps the two wing petals. Two wing petals overlaps the margins of two keel petals which are internal. e.g. Pea
(v) Quinquncial: Two of the segments are completely internal. Other two of the segments are completely external. Remaining one segment has one margin overlapped another margin overlapping. e.g. Guava
Androecium
It is the third or the male whorl and is a collection of stamens.
Each stamen is a modified leaf or micosporophyll.
A stamen has two parts,
(i) Filament: A long slender stalk that carries food and water to anther.
(ii) Anther: It is a bilobed structure present at the tip of the filament. It bears four pollen sacs which are filled with tiny grains called pollen or pollen grains.
If the stamen is sterile and does not produce pollen grains, it is called staminode.
Types based on Adhesion among stamens:
(i) Epipetalous: The filament of the stamen is attached to the petals.
(ii) Epiphyllous: The filament of the stamen is attached to the tepal/perianth.
(iii) Polyandrous: The stamens are free from one another.
Types based on the Cohesion among stamens:
(i) Monadelphous: The filaments of all the stamens of a flower are fused to form a staminal tube. e.g. Hibiscus
(ii) Diadelphous: The filaments of the stamens are fused into two bundles. e.g. Pea
(iii) Polyadelphous: The stamens are united into more than two bundles,each with varied number of stamens. e.g. Citrus
(iv) Syngenesious: The anthers are all fused along their lateral margins, while the filaments are free. e.g. Sunflower
(v) Synandrous: Both the anthers and filaments of all the stamens are fused to form a column-like structure. e.g. Pumpkin
Types based on attachment of filament to the anthers:
(i) Basifixed: The filament is attached to the base of the anther. e.g. Mustard
(ii) Dorsifixed: The filament is attached to the back of the anther at the middle. e.g. Passiflora
(iii) Adnate: The filament is attached to the entire length of the anther. e.g. Magnolia
(iv) Versatile: The filament is attached at a point on the back of anther so that anther can freely move. e.g. Grass
Gynoecium
It is the fourth and the innermost whorl.
It is the female reproductive whorl and is composed of carpels.
Each carpel has three parts,
(i) Stigma: It is attached to style and receives the pollen grains.Its secretions stimulate germination of pollen grains.
(ii) Style: It form the neck of the carpel to which stigma is attached. It exposes stigma for easy pollination.
(iii) Ovary: It is the swollen basal part of the carpel that contains one or more ovules. Each ovule encloses an embryo sac.
Apocarpous: The ovary is composed of two or more carpels and the carpels remain free.
Syncarpous: The ovary is composed of two or more carpels and the carpels are fused.
Placentation
Placentation refers to the mode of arrangement of placenta and the ovules within ovary.
Placenta is the tissue with which ovules are attached to the wall of the ovary.
Types of Placentation
(i) Marginal: The placentae are found along the margins of the carpel. It is found in monocarpellary, unilocular ovary. Ex: Pea, bean
(ii) Axile: The margins of the carpels fuse to form a central axis on which the placentae develop. It is found in syncarpous ovaries. Ex: Citrus, Hibiscus
(iii) Parietal: The placentae develop on the ovary wall and the number of placentae is equal to the number of carpels. e.g. Cucurbita
(iv) Free-central: A single large swollen placenta arises from the base of the ovary. e.g. Primula
(v) Basal: It is seen in unilocular ovary, where a single placenta arises from the base of the ovary and bears a single ovule. e.g. Sunflower
.
Inflorescence is a cluster of flowers present on the same stalk called peduncle.
Depending upon the position on the stem, it could be terminal or axillary.
Types of inflorescence
| Racemose | Cymose |
|---|---|
| The main axis has unlimited growth; the terminal bud continues to grow. | The main axis has determinate growth; the terminal bud becomes a flower |
| The flowers are arranged in an acropetal succession, i.e. older flowers are at the base and younger flowers are towards the apex. | The flowers are arranged in a basipetal succession i.e. older flowers are at the apex and younger flowers are at the base. |
| Flower opening is centripetal. | Flower opening is centrifugal. |
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 |
Flower
A flower is the reproductive unit in angiosperms.The sexual reproduction in flowering plants is by the fusion of nuclei rather than cells and so the nuclei are termed as gametes.
Flower is a modified shoot with much condensed internodes and a number of appendages (floral leaves) at every node.
A flower is said to be a modified shoot for sexual reproduction.
Bract: a small leaf-like structure often positioned beneath a flower.
(i) Bracteate: a flower with a bract.
(ii) Ebracteate: a flower without bract.
Pedicel: the stalk of the flowers.
(i) Pedicellate: a flower with pedicel.
(ii) Sessile: a flower without pedicel.
Thalamus/Torus/Receptacle: the swollen end of the pedicel/axis, which bears floral leaves.
Complete flower: has all the four whorls.
Incomplete flower: one or more of the whorls is/are missing.
Bisexual/hermaphrodite flower: has both stamens and carpels.
Unisexual flower: has either stamens or carpels.
Staminate/male flower: only stamens are present.
Pistillate/female flower: only carpels are present.
Neuter flower: both stamens and carpels are absent.
Monoecious plant: bears both male and female flowers on the same pant. Ex: Maize, Castor bean
Dioecious plant: bears either male or female flowers. Ex: Papaya, Mulberry
Dichlamydeous flower: has both calyx and corolla
Monochlamydeous flower: has only one whorl; only corolla (asepalous) or only calyx(apetalous)
Actinomorphic/ radially symmetrical flower: flower can be cut into two identical halves, along any of the radii, passing through centre.
Zygomorphic: flower can be cut into two identical halves, only along one plane/radius, passing through centre. e.g. Pisum
Assymetrical: flower cannot be cut into two identical halves along any lane. e.g. Canna
Types of a Flower
Isomerous
It is the flower which has same number of floral leaves in each of the whorls.
(i) Dimerous: Floral leaves are in two's or multiples of it in each whorl.
(ii) Trimerous: Floral leaves are in threes or multiples of it in each whorl. e.g. flowers of monocots
(iii) Tetramerous: Floral leaves are in fours or multiples of it in each whorl. e.g. Brassicaceae
(iv) Pentamerous: Floral leaves are in fives or multiples of it in each whorl. e.g. most of the dicot flowers
Heteromerous
It is a flower which has different number of floral leaves in different whorls. e.g. member of Lamiaceae
Hypogynous
The ovary is situated on the trouts, above all other floral organs.
The ovary is superior.
Ex: Mustard, Tomato
Perigynous
The thalamus form a cup-like structure around the ovary and bears other floral organs almost at the same level on its rim.
The ovary is half superior or half inferior.
Ex: Rose, Pea
Epigynous
The thalamus form a cup which is fused with the ovary and all other floral organs arise on top of ovary.
The ovary is inferior.
Ex: Cucurbita, Sunflower
Parts of a Flower
A typical flower has four whorls namely,
(i) Calyx
(ii) Corolla
(iii) Androecium
(iv) Gynoecium/Pistil
Calyx
It is the first and the outermost whorl of a flower and it is composed of sepals.
It is generally green and leaf like and protects the flower bud before it opens.
The calyx may be polysepalous(sepals are free) or gamosepalous(sepals are fused together).
Corolla
It is the second whorl inner to sepals and is composed of petals.
It is generally large, brightly coloured and may have fragrance. They help in pollination by attracting insects.
The corolla may be polypetalous(petals are free from one another) or gamopetalous(petals are united together)
Perianth
The non-essential (non-reproductive) whorls of the flower constitute perianth.
The perianth is distinguished into an outer whorl of calyx and an inner whorl of corolla.
In other case, where perianth cannot be distinguished into calyx and corolla, the component segments are called tepals.
Aestivation
Aestivation refers to the arrangement of the segments of perianth in relation to one another in the bud condition.
Types of Aestivation
(i) Valvate: The margins of the sepals/petals/tepals just touch one another but there is no overlapping. e.g. Calatropis
(ii) Twisted/Contorted: One margin of each of the sepal/petals/tepals overlaps the margin of the next member. e.g. Hibiscus
(iii) Ascendingly Imbricate: One of the sepal/petal is completely internal with both the margins being overlapped and one of the sepals/petals is completely external and remaining are in twisted pattern. e.g. Mustard
(iv) Descendigly Imbricate/Vexillary/Papilionaceous: The posterior petal, vexillum is completely external and overlaps the two wing petals. Two wing petals overlaps the margins of two keel petals which are internal. e.g. Pea
(v) Quinquncial: Two of the segments are completely internal. Other two of the segments are completely external. Remaining one segment has one margin overlapped another margin overlapping. e.g. Guava
Androecium
It is the third or the male whorl and is a collection of stamens.
Each stamen is a modified leaf or micosporophyll.
A stamen has two parts,
(i) Filament: A long slender stalk that carries food and water to anther.
(ii) Anther: It is a bilobed structure present at the tip of the filament. It bears four pollen sacs which are filled with tiny grains called pollen or pollen grains.
If the stamen is sterile and does not produce pollen grains, it is called staminode.
Types based on Adhesion among stamens:
(i) Epipetalous: The filament of the stamen is attached to the petals.
(ii) Epiphyllous: The filament of the stamen is attached to the tepal/perianth.
(iii) Polyandrous: The stamens are free from one another.
Types based on the Cohesion among stamens:
(i) Monadelphous: The filaments of all the stamens of a flower are fused to form a staminal tube. e.g. Hibiscus
(ii) Diadelphous: The filaments of the stamens are fused into two bundles. e.g. Pea
(iii) Polyadelphous: The stamens are united into more than two bundles,each with varied number of stamens. e.g. Citrus
(iv) Syngenesious: The anthers are all fused along their lateral margins, while the filaments are free. e.g. Sunflower
(v) Synandrous: Both the anthers and filaments of all the stamens are fused to form a column-like structure. e.g. Pumpkin
Types based on attachment of filament to the anthers:
(i) Basifixed: The filament is attached to the base of the anther. e.g. Mustard
(ii) Dorsifixed: The filament is attached to the back of the anther at the middle. e.g. Passiflora
(iii) Adnate: The filament is attached to the entire length of the anther. e.g. Magnolia
(iv) Versatile: The filament is attached at a point on the back of anther so that anther can freely move. e.g. Grass
It is the fourth and the innermost whorl.
It is the female reproductive whorl and is composed of carpels.
Each carpel has three parts,
(i) Stigma: It is attached to style and receives the pollen grains.Its secretions stimulate germination of pollen grains.
(ii) Style: It form the neck of the carpel to which stigma is attached. It exposes stigma for easy pollination.
(iii) Ovary: It is the swollen basal part of the carpel that contains one or more ovules. Each ovule encloses an embryo sac.
Apocarpous: The ovary is composed of two or more carpels and the carpels remain free.
Syncarpous: The ovary is composed of two or more carpels and the carpels are fused.
Placentation
Placentation refers to the mode of arrangement of placenta and the ovules within ovary.
Placenta is the tissue with which ovules are attached to the wall of the ovary.
Types of Placentation
(i) Marginal: The placentae are found along the margins of the carpel. It is found in monocarpellary, unilocular ovary. Ex: Pea, bean
(ii) Axile: The margins of the carpels fuse to form a central axis on which the placentae develop. It is found in syncarpous ovaries. Ex: Citrus, Hibiscus
(iii) Parietal: The placentae develop on the ovary wall and the number of placentae is equal to the number of carpels. e.g. Cucurbita
(iv) Free-central: A single large swollen placenta arises from the base of the ovary. e.g. Primula
(v) Basal: It is seen in unilocular ovary, where a single placenta arises from the base of the ovary and bears a single ovule. e.g. Sunflower
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