Question
Draw and describe the structure of a flower. Label the male and female reproductive parts, explaining the function of each.
(NCERT Class 12 Biology, Chapter 2 — Sexual Reproduction in Flowering Plants)
Solution — Step by Step
A flower has four whorls — sepals, petals, stamens, and carpels. Only the last two matter for reproduction. The stamen is the male whorl and the pistil (carpel) is the female whorl.
Each stamen has two parts:
- Filament — the stalk that holds the anther up, positioning it for pollination
- Anther — the bilobed sac where pollen grains (male gametophytes) are produced via meiosis
The anther is the functional unit. Without it, no pollen, no fertilisation.
The pistil (also called carpel) has three parts, each with a distinct job:
- Stigma — sticky surface at the top; receives pollen grains
- Style — the elongated tube connecting stigma to ovary; pollen tube grows through here
- Ovary — the swollen base containing one or more ovules, each with a female gametophyte (embryo sac)
Remember it top-down: S-S-O (Stigma → Style → Ovary).
After a pollen grain lands on the stigma, it germinates and the pollen tube grows down through the style into the ovary. There, it delivers two male gametes to the ovule — setting up double fertilisation, which is unique to angiosperms.
The ovary later becomes the fruit, and the ovule becomes the seed.
Why This Works
The flower’s architecture is a delivery system — every part is positioned to maximise the chance of pollen reaching the ovule. The anther sits high on the filament so wind or insects brush against it easily. The stigma is often sticky or feathery for the same reason: maximum pollen capture.
The style isn’t just a passive tube. It actively screens pollen — only compatible pollen (same species) can successfully grow a tube all the way to the ovary. This is why cross-species fertilisation doesn’t happen in nature.
The ovary wall protecting the ovules is also why angiosperms are so evolutionarily successful. Compare this to gymnosperms (like pine), where ovules are naked on cones — no ovary, no fruit.
Alternative Method — Memorising with a Diagram
If labelling a diagram is the question format (which it often is in CBSE boards), use this flow:
Anther (pollen)
|
Filament
←— STAMEN (male)
Stigma (receives pollen)
|
Style (pollen tube grows here)
|
Ovary → contains Ovule → becomes Seed
←— PISTIL (female)For NEET MCQs, remember: stamen = microsporophyll (produces microspores = pollen), carpel = megasporophyll (produces megaspores = embryo sac). These terms appear in plant kingdom questions and confuse students who only memorised the flower-level names.
A bisexual flower has both stamens and pistil in the same flower (e.g., Hibiscus). A unisexual flower has only one (e.g., Papaya — male and female flowers on separate plants = dioecious). This distinction is a favourite 1-mark board question.
Common Mistake
Students write “pollen is produced in the filament” — this is wrong. The anther produces pollen. The filament is just the stalk. Similarly, many mix up stigma and style: stigma is the tip (receives pollen), style is the tube below it. In a diagram question, swapping these two costs you a mark.
Another slip: calling the entire female structure the “pistil” when the question asks about a single carpel. A pistil can be made of one or many fused carpels. In NCERT, both terms are used — use carpel when talking about a single unit, pistil when talking about the whole female organ.
Final answer summary:
| Part | Belongs To | Function |
|---|---|---|
| Anther | Stamen (male) | Produces pollen grains |
| Filament | Stamen (male) | Supports anther |
| Stigma | Pistil (female) | Receives pollen |
| Style | Pistil (female) | Pollen tube pathway |
| Ovary | Pistil (female) | Contains ovules; becomes fruit |