Plant reproduction

1. Purpose of Flowers

  • Reproductive organ of angiosperms

  • Functions:

    • Produce gametes

    • Enable fertilization

    • Form seeds and fruits

  • Often adapted for pollination (color, scent, nectar)

2. Flower Structure (Core)

Structure

Function

Sepals (calyx)

protect bud

Petals (corolla)

attract pollinators

Stamen (male)

produce pollen

Carpel/Pistil (female)

produce ovules, receive pollen

3. Male vs Female Structures

Stamen (male)

  • Anther → produces pollen (male gametophyte)

  • Filament → supports anther

Carpel/Pistil (female)

  • Stigma → receives pollen

  • Style → pathway for pollen tube

  • Ovary → contains ovules

  • Ovule → becomes seed

4. Flower Types

Complete vs Incomplete

  • Complete: all 4 parts present

  • Incomplete: missing ≥1 part

Perfect vs Imperfect

  • Perfect: both male + female

  • Imperfect: only one sex

Monoecious vs Dioecious

  • Monoecious: both sexes on same plant

  • Dioecious: sexes on different plants

5. Pollination vs Fertilization

Pollination

  • Transfer of pollen → stigma

  • Methods:

    • Wind

    • Animals (insects, birds, bats)

Fertilization

  • Fusion of sperm + egg

Critical distinction

  • Pollination ≠ fertilization

6. Angiosperm Life Cycle (Core Sequence)

A. Male Side (Anther)

  • Diploid cell → meiosis → 4 haploid spores

  • Each → pollen grain (male gametophyte)

  • Mitosis → 2 nuclei (sperm)

B. Female Side (Ovule)

  • Diploid cell → meiosis

  • 1 survives → mitosis → 8 nuclei embryo sac

  • Contains:

    • Egg cell

    • Polar nuclei

C. Pollination → Fertilization

  1. Pollen lands on stigma

  2. Pollen tube grows down style

  3. Sperm travel to ovule

7. Double Fertilization (Key AP Concept)

  • Sperm 1 + egg → diploid zygote (2n)

  • Sperm 2 + 2 polar nuclei → triploid endosperm (3n)

Significance

  • Endosperm = nutrient supply

  • Forms only if fertilization occurs → efficient

8. After Fertilization

Structure

Becomes

Ovule

Seed

Ovary

Fruit

Zygote

Embryo

Endosperm

Nutrient tissue

9. Seed Dispersal

Methods

  • Wind (light, winged seeds)

  • Water (buoyant seeds)

  • Animals:

    • Stick to fur

    • Eaten → excreted

    • Buried (e.g., squirrels)

10. Germination

Conditions:

  • Water

  • Oxygen

  • Proper temperature

Process:

  • Seed absorbs water → swells → coat breaks

  • Radicle (root) emerges first

  • Shoot grows upward

11. Monocot vs Dicot Germination

Feature

Monocot

Dicot

Cotyledons

1

2

Position

stays underground

may emerge

Function

protection

protection or photosynthesis

12. Fruit Types

Type

Description

Example

Simple

one ovary

tomato

Aggregate

multiple ovaries, one flower

blackberry

Multiple

multiple flowers fuse

pineapple

13. Asexual (Vegetative) Reproduction

No seeds, no fertilization.

Structures

  • Bulbs (onion)

  • Tubers (potato)

  • Stolons (strawberry)

  • Roots/leaves (sweet potato, Bryophyllum)

Key

  • Produces genetically identical clones

14. High-Yield Concepts

  • Flower = reproductive system

  • Double fertilization is unique to angiosperms

  • Endosperm = 3n

  • Ovule → seed, ovary → fruit

  • Structure = function:

    • Petals attract

    • Stigma captures

    • Ovary protects

15. Ultra-Condensed Chain

Meiosis → gametophytes → pollination → pollen tube → double fertilization → seed + fruit → dispersal → germination → new plant