Flowers

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Flowers
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What is the purpose of a flower?

• Helps guide insects to pollinating structures
• Attracts attention of animals

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Structures of flower
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External Structure
Sepals are the green parts that protect a flower
bud before it opens. There is usually one sepal
for each petal. All together the sepals are
called the calyx.   After the flower opens the
sepals can often still be seen behind the petals.
The sepals protect and sometimes support the
corolla.       
The petals are really advertisements for
insects, signaling "Nectar Here!" Nectar is
secreted at the base of the petals on the inside
of the flower. The nectar is used to lure insects
to the flower, and it is placed so that the
insects get a dusting of pollen as they crawl to
the nectar and lap it up. Then the insects fly
off to other flowers, taking the pollen from the
first flower with them.
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Male Structure

• The stamen is a long structure that contains a
  stalk and anther.
• The ANTHER is where the pollen develops.
• The stamen has a long, flexible stalk that moves
  easily in the wind, making the pollen easier to
  distribute to other flowers and/or reach the
  stigma.

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Female Structure

• The PISTIL is divided into three sections
• STIGMA- a sticky surface where pollen adheres
• STYLE- stalk that lifts the stigma to a position
  to get pollen
• OVARY- part that becomes the fruit and contains
  one or more undeveloped seeds (they will be
  developed as the pollen, containing the sperm
  cell , reaches the ovary)

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How pollen gets to the stigma

• Pollination by animals

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How petals lead insects to the pollen
bullseye
stripe
shape
composite
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Pollination by water
Flowers are on long stalks that poke out of the
water the male releases pollen underwater, which
floats to the surface. Some might eventually fly
up to the flowers.
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Male and female flowers
Male and female begonia flowers have different
flowers. Males have a cluster of stamens, which
contain pollen delivered by wind to the female
stigmas.
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Self-pollination
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Cross Pollination
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Why would a plant want to cross-pollinate???

• Gain genetic advantage over disease
• Look different
• Some cannot self-pollinate