Sexual Reproduction in
Flowering Plants
~ Class 12th Biology Notes ~
Board: CBSE (NCERT)
Subject: Biology | Chapter: Sexual Reproduction in Flowering Plants (NCERT Ch.
2)
✏ Style: Handwritten notebook notes with labelled diagrams
Covers: Flower structure, Pollen & Ovule, Pollination, Double Fertilization,
Embryo/Seed/Fruit development
Topic 1
, Topic 1
1. Introduction — The Flower
The flower is the site of sexual reproduction in angiosperms (flowering plants). Flowers
show incredible diversity in size, colour, shape and structure — all of which are usually
adaptations related to their mode of pollination.
Bisexual vs Unisexual Flowers
Term Meaning Example
Hibiscus,
Bisexual Flower has BOTH stamens (male) and pistil (female)
Mustard
Flower has only ONE of the two — either male (staminate) or Papaya,
Unisexual
female (pistillate) Cucumber
Monoecious vs Dioecious Plants
Monoecious — both male and female unisexual flowers are present on the same
plant. E.g. maize, cucumber, castor.
Dioecious — male and female flowers are present on different (separate) plants. E.g.
papaya, date palm, mulberry.
Homogamy vs Heterogamy
Homogamous flower = anther and stigma mature at the same time (favours self-
pollination).
Heterogamous / Dichogamous flower = anther and stigma mature at different
times (favours cross-pollination) — further divided into protandry (anther matures
first) and protogyny (stigma matures first).
Topic 2
, Topic 2
2. Structure of a Typical Flower
A typical flower has 4 whorls, attached to a stalk called the pedicel, which is swollen at
the tip into the thalamus (receptacle):
Anther Stigma
Filament (Androecium) Style
Petal (Corolla)
Ovary (Gynoecium)
Sepal (Calyx)
Thalamus
Pedicel
Fig 2.1 — The four whorls of a typical flower
Whorl Nature Function
Outermost, usually
Calyx (sepals) Protects the flower bud
green
Often brightly
Corolla (petals) Attracts pollinators (insects, birds)
coloured
Androecium Male reproductive
Produces pollen grains (male gametes)
(stamens) whorl
Gynoecium Female reproductive Produces ovules (female gametes) & becomes
(pistil/carpel) whorl the fruit
Calyx + Corolla together form the perianth (non-reproductive, accessory whorls);
Androecium + Gynoecium are the essential (reproductive) whorls.
Topic 3
Flowering Plants
~ Class 12th Biology Notes ~
Board: CBSE (NCERT)
Subject: Biology | Chapter: Sexual Reproduction in Flowering Plants (NCERT Ch.
2)
✏ Style: Handwritten notebook notes with labelled diagrams
Covers: Flower structure, Pollen & Ovule, Pollination, Double Fertilization,
Embryo/Seed/Fruit development
Topic 1
, Topic 1
1. Introduction — The Flower
The flower is the site of sexual reproduction in angiosperms (flowering plants). Flowers
show incredible diversity in size, colour, shape and structure — all of which are usually
adaptations related to their mode of pollination.
Bisexual vs Unisexual Flowers
Term Meaning Example
Hibiscus,
Bisexual Flower has BOTH stamens (male) and pistil (female)
Mustard
Flower has only ONE of the two — either male (staminate) or Papaya,
Unisexual
female (pistillate) Cucumber
Monoecious vs Dioecious Plants
Monoecious — both male and female unisexual flowers are present on the same
plant. E.g. maize, cucumber, castor.
Dioecious — male and female flowers are present on different (separate) plants. E.g.
papaya, date palm, mulberry.
Homogamy vs Heterogamy
Homogamous flower = anther and stigma mature at the same time (favours self-
pollination).
Heterogamous / Dichogamous flower = anther and stigma mature at different
times (favours cross-pollination) — further divided into protandry (anther matures
first) and protogyny (stigma matures first).
Topic 2
, Topic 2
2. Structure of a Typical Flower
A typical flower has 4 whorls, attached to a stalk called the pedicel, which is swollen at
the tip into the thalamus (receptacle):
Anther Stigma
Filament (Androecium) Style
Petal (Corolla)
Ovary (Gynoecium)
Sepal (Calyx)
Thalamus
Pedicel
Fig 2.1 — The four whorls of a typical flower
Whorl Nature Function
Outermost, usually
Calyx (sepals) Protects the flower bud
green
Often brightly
Corolla (petals) Attracts pollinators (insects, birds)
coloured
Androecium Male reproductive
Produces pollen grains (male gametes)
(stamens) whorl
Gynoecium Female reproductive Produces ovules (female gametes) & becomes
(pistil/carpel) whorl the fruit
Calyx + Corolla together form the perianth (non-reproductive, accessory whorls);
Androecium + Gynoecium are the essential (reproductive) whorls.
Topic 3
