Reproduction
Reproduction is the biological process by which organisms produce offspring of their own kind. The PMDC MDCAT 2026 syllabus expects you to compare alternation of generations across mosses, ferns and angiosperms, list types of asexual reproduction (with vegetative propagation), and walk step-by-step through sexual reproduction in flowering plants — including double fertilisation. Expect 2-4 MCQs.
Alternation of Generation
Plants and many algae alternate two distinct multicellular phases in their life cycle: a haploid gametophyte (n) that produces gametes by mitosis and a diploid sporophyte (2n) that produces haploid spores by meiosis.
- Gametophyte
- The haploid generation. Produces gametes by mitosis. Fusion of two gametes → diploid zygote.
- Sporophyte
- The diploid generation. Produces haploid spores by meiosis. Each spore germinates into a new gametophyte.
The gametophyte is dominant: a green, photosynthetic moss plant with rhizoids, leaves and gametangia (antheridia + archegonia). The sporophyte is short-lived, attached to (and nutritionally dependent on) the gametophyte — a thin stalk with a capsule containing meiotically produced spores.
The sporophyte is dominant — the leafy fern we recognise. The gametophyte (prothallus) is a small heart-shaped, free-living, photosynthetic structure that bears archegonia and antheridia. Water is still required for the flagellated sperm to swim to the egg.
The sporophyte dominates overwhelmingly. The gametophyte is reduced to microscopic structures: the male gametophyte is the pollen grain (3 cells — 1 tube + 2 sperm), and the female gametophyte is the embryo sac (typically 7 cells, 8 nuclei, including the egg and the central cell with two polar nuclei). The female gametophyte is retained inside the ovule. No water is needed for fertilisation — pollen tubes do the job.
Asexual Reproduction
Asexual reproduction produces offspring genetically identical to the parent (clones) from a single individual — no fusion of gametes, no meiosis. It is fast and reliable but lacks genetic variation.
- Binary fission — in prokaryotes (e.g. E. coli) and many protists (Amoeba, Paramecium). Cell elongates and splits into two equal daughters.
- Budding — an outgrowth detaches as a new individual. Yeast (Saccharomyces), Hydra.
- Fragmentation — parent breaks into pieces, each regenerating a complete organism. Spirogyra, planaria, sea stars.
- Spore formation — haploid asexual spores from sporangia. Fungi (Rhizopus), ferns (sporophyte stage).
- Regeneration — replacement of lost parts; in some animals can give rise to new individuals.
- Parthenogenesis — development of an unfertilised egg. Honeybee drones, aphids, some lizards.
Natural and artificial methods that produce new plants from vegetative parts (root, stem, leaf):
- Runners / stolons — horizontal stems above ground (strawberry).
- Rhizomes — underground horizontal stems (ginger, turmeric).
- Tubers — swollen underground stems with eyes (potato).
- Bulbs — condensed shoots with fleshy leaves (onion, garlic).
- Corms — swollen underground stems (Colocasia, gladiolus).
- Leaves — Bryophyllum bears plantlets at leaf margins.
- Artificial methods — cuttings (rose, sugarcane), layering (jasmine), grafting (mango, citrus), tissue culture.
Sexual Reproduction in Plants
The flower is the reproductive structure of an angiosperm. A typical flower has four whorls: calyx (sepals), corolla (petals), androecium (stamens) and gynoecium (carpels/pistil).
A stamen = filament + anther. The anther bears four pollen sacs in which microspore mother cells undergo meiosis to give microspores → pollen grains (male gametophytes). A pistil = stigma + style + ovary. The ovary contains ovules; inside each ovule a megaspore mother cell undergoes meiosis to give 4 megaspores; one survives and divides mitotically (3 rounds) to form the 7-celled, 8-nucleate embryo sac (female gametophyte) — egg, two synergids, three antipodals, and a central cell with two polar nuclei.
Pollination
Transfer of pollen from anther to stigma. Self-pollination (within the same flower or plant) preserves traits but reduces variation; cross-pollination requires an agent — wind (anemophily), water (hydrophily), insects (entomophily), birds (ornithophily) — and increases genetic variation.
Once a pollen grain lands on a compatible stigma, it germinates a pollen tube through the style to the ovule. Two sperm cells are delivered:
- Sperm 1 + egg → diploid zygote (2n) → embryo.
- Sperm 2 + two polar nuclei → triploid endosperm (3n) — nutritive tissue for the embryo.
Hence "double" fertilisation. This is a defining feature of flowering plants.
Seed and fruit
After fertilisation the ovule matures into a seed and the ovary wall develops into the fruit (pericarp). A typical seed contains:
- Seed coat (testa + tegmen) from the integuments.
- Embryo — radicle (future root), plumule (future shoot), and one or two cotyledons (food store / first leaves).
- Endosperm — nutritive tissue (in monocots like wheat, corn it persists; in many dicots like beans the cotyledons absorb it).
Worked MCQs
Five MCQs covering the high-yield testing patterns for reproduction in plants.
Q1. In which of the following groups is the gametophyte the dominant generation?
Bryophytes (mosses, liverworts) are the only major land-plant group whose gametophyte is dominant. The familiar leafy moss is haploid; the sporophyte is a small attached stalk-and-capsule that depends on the gametophyte for nutrients.
Q2. The endosperm of a flowering-plant seed is typically:
In double fertilisation, one sperm fuses with two polar nuclei in the central cell to form the primary endosperm nucleus (1n + 2n = 3n). The endosperm therefore is triploid and stores starch, oils and proteins for the embryo.
Q3. A potato tuber is an example of which type of asexual reproduction?
A tuber is a swollen underground stem with axillary buds (the "eyes"). Each eye can sprout into a new plant — a textbook example of natural vegetative propagation. Budding is restricted to organisms like yeast and Hydra; potatoes do not "bud" in that sense.
Q4. The female gametophyte of a typical angiosperm consists of how many cells / nuclei?
A typical embryo sac has 7 cells and 8 nuclei: 1 egg + 2 synergids at the micropylar end, 3 antipodals at the chalazal end, and a single large central cell with 2 polar nuclei. The two polar nuclei combine with one sperm to form the 3n endosperm.
Q5. Which of the following is unique to angiosperms?
Double fertilisation — one sperm fertilising the egg and another fusing with the polar nuclei — is a hallmark of angiosperms. Photosynthesis, sexual reproduction and spore production are widespread across other plant and algal groups too.
Quick Recap
- Alternation of generations: gametophyte (n) ↔ sporophyte (2n).
- Mosses → gametophyte dominant. Ferns and seed plants → sporophyte dominant.
- Asexual types: binary fission, budding, fragmentation, spores, parthenogenesis, vegetative propagation.
- Vegetative propagation: runners, rhizomes, tubers, bulbs, corms; cuttings, layering, grafting, tissue culture.
- Pollen grain (3 cells) = male gametophyte; embryo sac (7 cells, 8 nuclei) = female gametophyte.
- Double fertilisation: sperm + egg → 2n zygote; sperm + 2 polar nuclei → 3n endosperm.
- Seed = embryo + endosperm + seed coat; fruit develops from the ovary wall.