This ppt deals with one of the unique features of angiosperms ie Double fertilization.

2. Plant kingdom
Plant kingdom is grouped into:
•Algae
•Bryophytes
•Pteridophytes
•Gymnosperms
•Angiosperms

3. Angiosperms
 The most diverse group of land plants
 These are the flowering plants
 Flower serves as the reproductive organs for the plants
 Flowers, endosperm within the seeds and the production of fruits
containing seeds are the distinguished features of this group
 Double fertilization is also one of the unique features of this group
Angiosperms mainly divide into two groups:
(I) Monocotyledons (II) Dicotyledons

4. Structure of a mature flower
A typical angiospermic flower may be
 Bisexual flower (male and female reproductive organs in the same
flower)
Unisexual (Either male or female reproductive organ present in the
flower)
Male reproductive organ is called Stamen (Anther & filament)
Female reproductive organ is Pistil (Ovary, style & stigma)

5. Fig: Structure of a mature bisexual flower showing its parts

6. Pistil/Carpel
• The female reproductive part of a
flower
• The pistil, centrally located, typically
consists of a swollen base, the ovary
• Which contains the potential seeds, or
ovules; a stalk, or style, arising from the
ovary; and a pollen-receptive tip
• The stigma, variously shaped and often
sticky.
Fig. showing structure of pistil

7. Stamen/Anther
•Stamen, the male reproductive part of
a flower
• The stamen consists of a long slender
stalk, the filament, with a two-lobed
anther at the tip
•The anther consists of four saclike
structures (microsporangia) that produce
pollen for pollination
•Pollen grains are known as male
gametophyte

8.  Double fertilization is a complex fertilization mechanism of flowering plants
(angiosperms)
 The process involves the joining of a female gametophyte
(megagametophyte, also called the embryo sac) with two
male gametes (sperm)
 It begins when a pollen grain adheres to the stigma of the carpel (the
female reproductive structure)
The pollen grain germinates to form pollen tube that extends down
towards the ovary through the style
The tip of the pollen tube then enters the ovary and penetrates through
the micropyle opening in the ovule
Double fertilization

9. Diagrammatic representation of double fertilization

10. Male gamete (n) Egg Nucleus (n) Zygote (2n) Embryo (2n)
Syngamy
Male gamete (n) Polar nuclei (2n) PEN (3n)
Triple Fusion
Syngamy Triple Fusion Double Fertilization
Unique feature of
Angiosperms
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11. Fig: Showing triple fusion
• The haploid sperm and haploid egg
combine to forma diploid zygote, the
process being called syngamy
• The other sperm and the
two haploid polar nuclei of the large
central cell of the megagametophyte
form a triploid nucleus (triple fusion)