A flower is the reproductive organ of angiosperms (flowering plants).
It is typically made of four whorls:
• Calyx (Sepals)
• Corolla (Petals)
• Androecium (Male reproductive whorl)
• Gynoecium (Female reproductive whorl)
1. Calyx (Sepals)
• Structure:
• Green, leaf-like structures forming the outermost whorl.
• Collectively called calyx.
• Function:
• Protect the flower bud before it opens.
• Sometimes photosynthetic, helping in food production.
2. Corolla (Petals)
• Structure:
• Brightly colored, delicate structures inside the calyx.
• Collectively called corolla.
• Function:
• Attract pollinators (insects, birds, bats).
• May secrete nectar.
• Protect reproductive organs in bud stage.
3. Androecium (Male Reproductive System)
• Made of stamens (male reproductive units).
• Each stamen has 2 parts:
• Anther:
• Bilobed, contains pollen sacs (microsporangia).
• Produces pollen grains (male gametophytes).
• Filament:
• Stalk that supports the anther.
, • Function:
• Production and release of pollen (male gametes).
4. Gynoecium (Female Reproductive System)
• Made of carpels (female reproductive units).
• Each carpel has 3 parts:
• Stigma
• Sticky surface at the tip.
• Function: Receives pollen during pollination.
• Style
• Slender stalk connecting stigma to ovary.
• Function: Pollen tube grows through style to reach ovule.
• Ovary
• Basal swollen part, contains ovules.
• Function: Produces ovules (female gametophytes). After fertilization,
ovary → fruit; ovule → seed.
🌱 Reproductive System Summary
• Male gametes: Produced in pollen grains (inside anthers).
• Female gametes: Produced in ovules (inside ovary).
• Pollination: Transfer of pollen to stigma (self or cross).
• Fertilization: Fusion of male gamete (from pollen) with female gamete (in ovule).
• Double fertilization (unique to angiosperms):
• One sperm fuses with egg → zygote (embryo).
• Other sperm fuses with polar nuclei → endosperm (nutritive tissue).
Part Structure Function
Sepals (Calyx) Green, leaf-like outer whorl Protects flower bud
Brightly colored, often
Petals (Corolla) Attract pollinators, protect inner whorls
fragrant
Stamen Anther (pollen sacs) + Produces and releases pollen (male
(Androecium) Filament gametes)
Female reproductive system; receives
Carpel/Pistil Stigma, Style, Ovary (with pollen, site of fertilization, forms fruit &
(Gynoecium) ovules) seeds
Pollen grains Male gametophytes, 2 cells Produce sperm cells
It is typically made of four whorls:
• Calyx (Sepals)
• Corolla (Petals)
• Androecium (Male reproductive whorl)
• Gynoecium (Female reproductive whorl)
1. Calyx (Sepals)
• Structure:
• Green, leaf-like structures forming the outermost whorl.
• Collectively called calyx.
• Function:
• Protect the flower bud before it opens.
• Sometimes photosynthetic, helping in food production.
2. Corolla (Petals)
• Structure:
• Brightly colored, delicate structures inside the calyx.
• Collectively called corolla.
• Function:
• Attract pollinators (insects, birds, bats).
• May secrete nectar.
• Protect reproductive organs in bud stage.
3. Androecium (Male Reproductive System)
• Made of stamens (male reproductive units).
• Each stamen has 2 parts:
• Anther:
• Bilobed, contains pollen sacs (microsporangia).
• Produces pollen grains (male gametophytes).
• Filament:
• Stalk that supports the anther.
, • Function:
• Production and release of pollen (male gametes).
4. Gynoecium (Female Reproductive System)
• Made of carpels (female reproductive units).
• Each carpel has 3 parts:
• Stigma
• Sticky surface at the tip.
• Function: Receives pollen during pollination.
• Style
• Slender stalk connecting stigma to ovary.
• Function: Pollen tube grows through style to reach ovule.
• Ovary
• Basal swollen part, contains ovules.
• Function: Produces ovules (female gametophytes). After fertilization,
ovary → fruit; ovule → seed.
🌱 Reproductive System Summary
• Male gametes: Produced in pollen grains (inside anthers).
• Female gametes: Produced in ovules (inside ovary).
• Pollination: Transfer of pollen to stigma (self or cross).
• Fertilization: Fusion of male gamete (from pollen) with female gamete (in ovule).
• Double fertilization (unique to angiosperms):
• One sperm fuses with egg → zygote (embryo).
• Other sperm fuses with polar nuclei → endosperm (nutritive tissue).
Part Structure Function
Sepals (Calyx) Green, leaf-like outer whorl Protects flower bud
Brightly colored, often
Petals (Corolla) Attract pollinators, protect inner whorls
fragrant
Stamen Anther (pollen sacs) + Produces and releases pollen (male
(Androecium) Filament gametes)
Female reproductive system; receives
Carpel/Pistil Stigma, Style, Ovary (with pollen, site of fertilization, forms fruit &
(Gynoecium) ovules) seeds
Pollen grains Male gametophytes, 2 cells Produce sperm cells
