Transcript Reproduction in Flowering Plants

The Parts of a Flower
• Most flowers have
four parts:
• sepals,
• petals,
• stamens,
• carpels.
The parts of a flower
• Sepals protect the
bud until it opens.
• Petals attract insects.
• Stamens make
pollen.
• Carpels grow into
fruits which contain
the seeds.
Stamen (male)
• Anther: pollen grains
grow in the anther.
• When the grains are
fully grown, the
anther splits open.
Pistil (female)
•
•
•
•
Stigma
Style
Carpel (ovary)
Ovules (eggs)
Pollination
• Flowering plants use
the wind, insects,
bats, birds and
mammals to transfer
pollen from the male
(stamen) part of the
flower to the female
(stigma) part of the
flower.
Pollination
• A flower is pollinated
when a pollen grain
lands on its stigma.
• Each carpel grows
into a fruit which
contains the seeds.
Fertilisation
• Pollen grains germinate
on the stigma, growing
down the style to reach
an ovule.
• Fertilised ovules develop
into seeds.
• The carpel enlarges to
form the flesh of the fruit
and to protect the ovary.
Wind pollination
• Some flowers, such as
grasses, do not have
brightly coloured petals
and nectar to attract
insects.
• They do have stamens
and carpels.
• These flowers are
pollinated by the wind.
Seed dispersal
Seeds are dispersed in
many different ways:
• Wind
• Explosion
• Water
• Animals
• Birds
• Scatter
How birds and animals help
seed dispersal
• Some seeds are
hidden in the ground
as a winter store.
• Some fruits have
hooks on them and
cling to fur or clothes.
How birds and animals help
seed dispersal
• Birds and animals eat
the fruits and excrete
the seeds away from
the parent plant.
Sexual Reproduction
• Calyx-the outermost and often
green color. Individual calyxsepals-Protects inner whorls
at bud stage
• Corolla-next inner whorl and is
often colored brightly, Individuals-Petals
• Anther has 4 pollen sacs, one
in each lobe. Pollen sacs
contain the mother cells,
which undergo meiosis. Each
microspere mother cell
produces 8 sperm cells.
Asexual Reproduction
• In some species, stems arch over
and take root at their tips,
forming new plants. The
horizontal above-ground stems
(called stolons) of the strawberry
(shown here) produce new
daughter plants at alternate
nodes.
• Underground stems
• rhizomes
• bulbs
• corms and
• tubers
• are used for asexual reproduction
as well as for food storage. Irises
and day lilies, for example, spread
rapidly by the growth of their
rhizomes.
Asexual Reproduction
• This photo shows the
leaves of the common
ornamental plant
Bryophyllum (also called
Kalanchoë) . Mitosis at
meristem along the leaf
margins produce tiny
plantlets that fall off and
can take up an
independent existence
Asexual Reproduction
• Some plants use their roots for asexual reproduction. The dandelion is a
common example. Trees, such as the poplar or aspen, send up new stems
from their roots. In time, an entire forest of trees may form — all part of a
clone of the original tree.
• Apple seeds are planted only for the root and stem system that grows
from them. After a year's growth, most of the stem is removed and a twig
(scion) taken from a mature plant of the desired variety is inserted in a
notch in the cut stump
• Citrus trees and many other species of angiosperms use their seeds as a
method of asexual reproduction; a process called apomixis.
• In one form, the egg is formed with 2n chromosomes and develops
without ever being fertilized.
• In another version, the cells of the ovule (2n) develop into an embryo
instead of the fertilized egg.