A flower is not just a beautiful, colourful part of a plant; it is actually its reproductive organ. Its primary purpose is to facilitate sexual reproduction, which leads to the formation of fruits and seeds, ensuring the continuation of the plant species. A typical flower is attached to the stem by a stalk called the pedicel, with the swollen top end known as the thalamus. The floral parts are arranged in four distinct whorls on this thalamus. From the outermost to the innermost, these are the calyx (made of sepals), the corolla (made of petals), the androecium (the male part made of stamens), and the innermost gynoecium (the female part made of carpels). Flowers that contain both androecium and gynoecium are called bisexual flowers, while those missing one of these are termed unisexual.
The male reproductive part, the androecium, is composed of stamens. Each stamen consists of a thin stalk called the filament and a broader, bilobed structure at the top known as the anther. Inside the anther lobes are pollen sacs which produce numerous microscopic pollen grains. These pollen grains are the male gametes and are crucial for fertilization. On the other hand, the female reproductive part, the gynoecium or pistil, is located in the centre of the flower. A carpel is made up of three parts: the sticky stigma at the top to catch pollen, a long tube-like style, and a swollen base called the ovary. The ovary contains ovules, each of which holds an egg cell, the female gamete.
The process of pollination, which is the transfer of pollen grains from the anther to the stigma, is a key event. This can happen within the same flower (self-pollination) or between different flowers (cross-pollination), often aided by agents like wind, water, insects, or birds. Following successful pollination, a pollen tube grows from the pollen grain down through the style to reach the ovary. The male gamete then travels through this tube to fuse with the egg cell inside an ovule, in a process called fertilization. This fusion forms a zygote, which develops into an embryo inside the seed. Meanwhile, the ovary itself ripens and transforms into a fruit, protecting the seeds until they are ready to grow into new plants, thus completing the reproductive cycle.
Multiple choice type
Question 1.
Bougainvillea flower is an example of
- incomplete flower
- having a large nectary
- water pollination
- large colourful bracts
Question 2.
A flower is said to be complete when:
- It has the corolla and calyx
- It has the corolla and gynoecium
- It has the androecium and gynoecium
- It has all the four whorls
Question 3.
The part of the flower that gives rise to the fruit is
- Sepals
- Petals
- Ovary
- Stamens
Question 4.
The part of the flower that gives rise to the seed is
- Ovary
- Placenta
- Ovule
- Pollen grain
Question 5.
The essential whorls of a flower are the
- Calyx and corolla
- Stamen and ovary
- Calyx and epicalyx
- Androecium and gynoecium
- Very short answer type
Match the parts in Column A with the flowers or parts of the flower in Column B.
| Column A | Column B |
| (a) Polyadelphous | (i) Polypetalous |
| (b) Pollen grains | (ii) Calyx, corolla |
| (c) Free petals | (iii) Nectar |
| (d) Non-essential | (iv) Bombax |
| (e) Sweet fragrant fluid | (v) Pollen sac |
Ans:
| Column A | Column B |
| (a) Polyadelphous | (iv) Bombax |
| (b) Pollen grains | (v) Pollen sac |
| (c) Free petals | (i) Polypetalous |
| (d) Non-essential | (ii) Calyx, corolla |
| (e) Sweet fragrant fluid | (iii) Nectar |
- Short answer type
Question 1.
1. Explain the following term: Incomplete flower
2. Explain the following term: Staminate flower
3. Explain the following term: Pistillate flower
4. Explain the following term: Bisexual flower
Ans:
Flower Terminology
1. Incomplete Flower
An incomplete flower is any flower that lacks one or more of the four floral whorls (or parts): the calyx (sepals), the corolla (petals), the androecium (stamens), or the gynoecium (carpels/pistil).
- Example: A flower that lacks petals (corolla) or a flower that lacks stamens is considered incomplete.
2. Staminate Flower
A staminate flower is a flower that possesses only the male reproductive parts (the androecium, or stamens) and lacks the female parts (the pistil/carpels).
- Characteristic: Staminate flowers are always unisexual and are often referred to as male flowers.
3. Pistillate Flower
A pistillate flower is a flower that possesses only the female reproductive parts (the gynoecium, or pistil/carpels) and lacks the male parts (the stamens).
- Characteristic: Pistillate flowers are always unisexual and are often referred to as female flowers.
4. Bisexual Flower
A bisexual flower (also called a perfect flower or hermaphrodite flower) is a flower that possesses both male and female reproductive organs—the androecium (stamens) and the gynoecium (pistil/carpels)—in the same flower structure.
- Characteristic: These flowers are complete in terms of essential organs and can usually self-pollinate.
Question 2.
1. Distinguish between the following pairs: Flower and inflorescence
2. Distinguish between the following pairs: Petals and petaloid sepals
3.Distinguish between the following pairs: Polyandrous and polyadelphous androecium
Ans:
1. Flower and Inflorescence
| Feature | Flower | Inflorescence |
| Definition | The individual, reproductive unit of an angiosperm. | The arrangement or cluster of flowers on a floral axis (peduncle). |
| Components | Consists of accessory and essential whorls (sepals, petals, stamens, carpels). | Consists of the main floral axis, pedicels, and multiple individual flowers. |
| Function | Site of sexual reproduction and seed/fruit formation. | Facilitates efficient pollination by presenting many flowers conspicuously. |
2. Petals and petaloid sepals
| Feature | Petals | Petaloid Sepals |
| Origin/Whorl | Part of the Corolla (the second whorl). | Part of the Calyx (the first, outermost whorl). |
| Typical Appearance | Usually brightly colored, scented, or modified to attract pollinators. | Typically small, green, and protective. |
| Distinction | If sepals and petals are indistinguishable (usually brightly colored), they are collectively called Tepals. If the sepals themselves become large and brightly colored (like in Bougainvillea), they are called petaloid sepals. | The only difference is their position and evolutionary origin: they are derived from the outermost (calyx) whorl, despite their petal-like appearance. |
3. Polyandrous and polyadelphous androecium
| Feature | Polyandrous Androecium | Polyadelphous Androecium |
| Stamen State | The stamens are all free and completely separate from one another. | The stamens are united or fused by their filaments into three or more distinct bundles or groups. |
| Etymology | Poly (many) + Andros (male/stamen). | Poly (many) + Adelphos (brother/bundle). |
| Example | Found in flowers like Petunia and many types of Ranunculus. | Found in flowers like Citrus (Lemon, Orange). |
Question 3.
1.Where is the following structure/part located and what are its functions? Placenta
2. Where are the following structures/parts located and what are their functions? Thalamus
3. Where are the following structures/parts located and what are their functions? Anther
4. Where are the following structures/parts located and what are their functions? Stigma
Ans:
1. Placenta
| Feature | Description |
| Location | Located inside the uterus of a pregnant female mammal. It develops from the tissues of both the mother and the embryo, temporarily attaching the fetus to the uterine wall. |
| Functions | Acts as the vital interface between mother and fetus. Key functions include: Nutrition and Respiration: Transfers oxygen and nutrients (glucose, amino acids) from the maternal blood to the fetal blood. Excretion: Carries waste products (like urea and CO2) from the fetal blood to the maternal blood for disposal. Endocrine: Produces hormones (e.g., hCG, progesterone) necessary to maintain the pregnancy. |
2. Thalamus
| Feature | Description |
| Location | Located deep within the forebrain, just above the brainstem and nestled between the cerebral cortex and the midbrain. |
| Functions | Serves as the major relay station and integrator for most sensory and motor signals traveling to and from the cerebral cortex. It filters, sorts, and transmits information concerning touch, sight, sound, and taste, essentially acting as the brain’s “switchboard.” |
3. Anther
| Feature | Description |
| Location | The top, sac-like part of the stamen (the male reproductive organ of a flower). It is usually supported by a long, thin stalk called the filament. |
| Functions | The primary site of pollen production. It contains pollen sacs where male gametes (pollen grains) are formed through meiosis. |
4. Stigma
| Feature | Description |
| Location | The uppermost tip of the pistil/carpel (the female reproductive organ of a flower). It is typically elevated on a stalk called the style. |
| Functions | Serves as the receptive surface for pollen grains during pollination. It is often sticky or feathery to effectively catch and trap pollen. |
Question 4.
1. are the following described as stated: The androecium of pea flower is diadelphous 2. Why are the following described as stated: Ray florets of sunflowers are neuters.
3. Why are the following described as stated: Salvia sepals are petaloid.
Ans:
1. Androecium of Pea Flower is Diadelphous
The androecium (male whorl, or stamens) of a pea flower is described as diadelphous because the filaments of its ten stamens are fused together to form two separate bundles (or groups).
- Structure: Nine stamens are typically fused together to form one tube or sheath, while the tenth stamen remains free. This forms the characteristic $9 + 1$ arrangement, which constitutes two distinct bundles.
- Significance: The prefix di- means “two,” and -adelphous means “brotherhood” or “bundle.”
2. Ray Florets of Sunflowers are Neuters
The ray florets (the large, petal-like structures on the outer rim of the flower head) of sunflowers are described as neuters because they do not possess either the male (androecium) or the female (gynoecium) reproductive organs.
- Function: Ray florets are sterile. Their sole biological role is to be large and conspicuous to attract pollinating insects to the central, tiny disc florets, which are fertile.
- Significance: A neuter flower is one that is missing both essential (reproductive) whorls, making it unable to produce gametes.
3. Salvia Sepals are Petaloid
The sepals (the outermost whorl, typically green) of the Salvia flower (like those in the sage family) are described as petaloids because they are large, brightly colored, and look like petals.
- Appearance: Instead of being small and green (foliaceous), the sepals are brightly colored, often blue or purple, making them indistinguishable from or more prominent than the true petals.
- Function: By being conspicuous and colorful, the petaloid sepals take over the function of the petals, which is attracting pollinators.
- Long answer type
Question 1.
Name the different types of androecium found in flowers.
Ans:
The different types of androecium (the male reproductive part of a flower, consisting of the stamens) are primarily classified based on the fusion or coherence of the stamens, and sometimes by the length of the filaments.
Here are the main types based on fusion:
Fusion of Stamens
- Monadelphous (Single Bundle)
- Description: Filaments of all stamens are united to form a single tube or column, but the anthers remain free.
- Example: China rose (Hibiscus).
- Diadelphous (Two Bundles)
- Description: Filaments are united to form two distinct bundles. The common pattern is , where nine are fused, and one stamen remains free.
- Example: Pea (Pisum sativum) and other legumes.
- Polyadelphous (Many Bundles)
- Description: Filaments are united into more than two bundles.
- Example: Citrus (Orange, Lemon) and silk cotton (Bombax).
- Syngenesious (Anthers Fused)
- Description: The anthers are fused together to form a tube, but the filaments remain free.
- Example: Sunflower and other members of the Asteraceae family.
- Synandrous (Complete Fusion)
- Description: Both filaments and anthers are completely fused together.
- Example: Members of the gourd family (Cucurbitaceae).
Length of Stamens
- Didynamous
- Description: There are four stamens in total, arranged in two pairs of unequal length (two long and two short).
- Example: Salvia and Snapdragon.
- Tetradynamous
- Description: There are six stamens in total, arranged in two whorls of unequal length (four long inner stamens and two short outer stamens).
- Example: Mustard (Brassica) and other members of the Brassicaceae family.
Question 2.
1. Name the type of androecium found in china rose.
2. Name the type of androecium found in bombax .
3. Name the type of androecium found in pea.
Ans:
Here are the types of androecium (stamen arrangement) found in the specified flowers:
- China Rose (Hibiscus): Monadelphous
- (Filaments of all stamens are united into one single tube).
- Bombax (Silk Cotton Tree): Polyadelphous
- (Filaments are united into more than two separate bundles).
- Pea (Pisum sativum): Diadelphous
- (Filaments are united into two bundles, typically 9 in one and 1 free).
- Structured/Application/Skill type
Question 1.
The figure given alongside represents a generalized arrangement of the different parts of a bisexual flower. Name the parts numbered 1-10.
Ans:
| Label Number | Name of Part |
| 1 | Anther |
| 2 | Filament |
| 3 | Ovary (The enlarged basal part of the pistil) |
| 4 | Ovules (Inside the ovary) |
| 5 | Stigma |
| 6 | Style |
| 7 | Petal (Corolla) |
| 8 | Sepal (Calyx) |
| 9 | Nectary (or Nectaries/Glands at the base) |
| 10 | Thalamus (or Receptacle) |
Question 2.
1.Given below are two figures (A and B) of a certain part of a flower. Study the figures carefully and answer the following question:
Which major organ of a flower does the figure A represent? What is the collective term for this organ?
2. Given below are two figures (A and B) of a certain part of a flower. Study the figures carefully and answer the following question:
Are the contents of the pollen sacs in B male or female?
3. Given below are two figures (A and B) of a certain part of a flower. Study the figures carefully and answer the following question:
Can you state how the contents of the pollen sacs would come out?
Ans:
1. Organ Representation and Collective Term
The figure A represents the Stamen, which is the male reproductive organ of a flower.
The collective term for all the stamens in a single flower is Androecium.
2. Contents of the Pollen Sacs
The contents of the pollen sacs in Figure B are male.
The pollen sacs contain pollen grains, which hold the male gametes (or male nuclei) necessary for plant reproduction.
3. How the Contents Come Out
The contents of the pollen sacs (the pollen grains) come out through the process of dehiscence.
- Mechanism: When the anther matures and dries, the wall of the anther, particularly along specific lines of weakness (the stomium), splits open or ruptures.
- Result: This mechanism releases the mature pollen grains, making them available for transfer to the stigma of the same or another flower during pollination.
Question 3.
What are bracts? State their function.
Ans:
Bracts are specialized, often leaf-like structures that differ significantly in color, size, and shape from the foliage leaves, and are found at the base of a flower or a cluster of flowers (inflorescence).
Definition and Location
A bract is a modified leaf subtending (located just below) the flower or flower stalk (pedicel) in the axis of which the flower arises.
- In some plants, bracts are small and scale-like.
- In others, they can be large, highly colored, and petal-like, resembling the petals themselves (e.g., Bougainvillea, Poinsettia).
Function of Bracts
The function of bracts depends on their form, but their two primary roles are protection and attraction:
- Protection (When small or green):
- They enclose and protect the flower bud or young inflorescence before it opens, shielding the delicate reproductive parts from mechanical injury, harsh weather, and herbivores.
- Attraction (When large and colorful):
- In flowers where the true petals (corolla) are small, absent, or inconspicuous, the large, brightly colored bracts take on the role of the petals. They function to attract pollinators (insects, birds, etc.) to the flower, ensuring successful pollination.
Question 4.
Explain the terms Monadelphous, Diadelphous and Polyadelphous. In each case name a flower possessing such an androecium.
Ans:
| Term | Explanation | Example Flower |
| Monadelphous | The filaments of all the stamens are united to form a single tube or bundle, but the anthers remain free. (Mono- means one, -adelphous means brotherhood/bundle.) | China Rose (Hibiscus) |
| Diadelphous | The filaments are united into two separate bundles or groups. In a pea flower, this is typically seen as nine stamens fused together and one stamen remaining free (9 + 1 arrangement). (Di- means two.) | Pea (Pisum sativum) |
| Polyadelphous | The filaments are united into more than two separate bundles or groups. (Poly- means many.) | Bombax (Silk Cotton Tree) |
