Transcript Sexual Reproduction in Plants

Sexual Reproduction
in Plants
The Seed
 The seed is the product of sexual reproduction
in most plants.
 The seed contains an embryo, a food supply
and a seed coat that keeps it from drying out.
 Seed-bearing plants can be classified into two
groups based on seed structure.
 The two groups are called Angiosperms and
Gymnosperms.
Angiosperms
 Angiosperms are
flowering plants
 The seeds form
inside the flower
 When mature the
seeds are enclosed
in a case.
Sexual Reproduction in
Angiosperms
 The flowers produced by angiosperms
contain the plant’s reproductive organs
 The female reproductive organs are
called the pistil
 The male reproductive organs are called
the stamen
Pollination
 In order for the seeds
to develop, pollen
grains from the
anthers must reach
the stigma of the
pistil.
 This process is
called pollination
 There are two types of pollination used
by angiosperms;
 Self-pollination - the males and female
gametes come from the same plant
 Cross –pollination – the male and female
gametes come from two different plants. The
two most common agents of crosspollination are wind and insects.
Fertilization
 The pollen grain
must grow a pollen
tube to reach the
ovule
 When the pollen
reaches the ovule a
zygote and a
cotyledon are
formed.
 The cotyledon
contains stored food.
Gymnosperms
 Gymnosperms do
not produce flowers
 Produce seeds
inside the cones
 Seeds have a coat
that protects them
but are not inside a
case
Sexual Reproduction in
Gymnosperms
 Gymnosperms produce their seeds
inside cones. For this reason they are
called conifers.
 In some species male and female cones
are produced on separate trees.
 In most conifers male and female cones
are produced by each tree.
Pollination and
Fertilization
 Pollination proceeds
the same as in
angiosperms
 Fertilization also
requires the
formation of a pollen
tube to allow the
pollen to reach the
egg.
Plants without seeds
 Plants such as
mosses and ferns
reproduce through
spores
 Like gametes
spores are haploid
however, a spore
can develop into a
new plant without
fertilization.
 The mature form called a sporophyte will
release the spores
 Under the correct conditions the spore will
develop into a gametophyte.
 The two main advantages for dispersal are;
that they are light and that they can survive
unfavourable conditions by staying dormant
until the conditions are ideal.