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STRUCTURE OF A FLOWER
•Flowers are reproductive organs
that are composed of four kinds of
specialized leaves:
1. Petals
2. Sepals
3. Stamens
4. Carpels (also called Pistils)
Petals – Brightly colored structure
just inside the sepals; attracts insects
and other pollinators to a flower.
Sepals – Outermost circle of flower
parts that encloses a bud before it
opens and protects the flower while
it is developing.
Pistil (also called carpel) –
Female part of a plant;
Innermost part of a flower
that produces the female
gametophyte.
•Stigma- Sticky portion
located at the top of the style
where pollen frequently
lands
•Broad base forms an ovary,
which contains one or more
ovules (contains eggs inside)
•The diameter of the carpel
narrows into a stalk called a
style.
STYLE
STIGMA
PISTIL OR CARPAL
Complete Flower – Has all
four organs
Incomplete Flower – Lacks
one or more organs
POLLINATION
Pollination – Transfer of pollen from the stamen to
the pistil.
Methods of Pollination:
1. Wind
2. Animals (most are
pollinated by animals)
Pollination Adaptations That Attract Animals:
1. Nectar
2. Petal Color
3. Scent
TYPES OF POLLINATION
Self-Pollination – Stigma receives pollen from the
same plant.
Cross-Pollination – Pollen
from one plant is carried to the
stigma of another plant.
-Must be same type of plant.
-Allows for exchange of
genetic material
Reproduction in Flowers
Similar to Gymnosperms Since:
1. Both produce seeds
2. Gametophytes are within the body of the
sporophyte.
FERTILIZATION IN FLOWERS
1. Pollen grain lands on the stigma.
2. The pollen tube cell grows a tube to the ovary.
3. The two sperm cells move through the tube into the ovule.
•One sperm joins with the egg in the ovule.
•The other joins with the central cell (2N) to form the endosperm
(3N)
•The process is called double fertilization.
•Double Fertilization - Fertilization in angiosperms, in
which two distinct fertilization events take place between
the male and female gametophyte.
SEED FORMATION
1. After fertilization occurs, the flower dies and the
seed develops.
2. Ovule becomes the seed coat which protects the
embryo.
3. The zygote divides becoming the embryo.
4. The 3N central cell develops into the endosperm
which is food-storage tissue.
FRUITS
The ovary develops into the
fruit, which can be dry or
fleshy.
Fruits protect the seeds and
aid in dispersal.
Dry
Examples: Nuts and Grains
Fleshy
Examples: Oranges, Peaches,
Tomatoes, Squash
SEED
GERMINATION
Seeds can remain dormant
until conditions are right for
development and growth.
-Water, oxygen, and
favorable temperatures
are usually needed.
Germination – Early plant
stage of a plant embryo.
- Germination is the development
of the seed into a new plant.
During growth, the roots appears first,
then the stem, and finally the leaves.
GROWTH AND DEVELOPMENT
Plants respond to stimuli from the environment. This
process is called TROPISM.
Positive Tropism - Growth towards the stimulus.
Negative Tropism – Growth away from the stimulus
Phototropism – Growth towards
light
Gravitropism – Response to gravity
Thigmotropism- response to touch
Phototropism- causes a plant to
grow towards a light source.
The experiment to the left
shows the importance of
apical meristems to the
growth of stems towards a
light source.
Geotropism (Gravitropism)causes the shoot of a germinating
seed to grow out of the soil (against
gravity). It also causes the roots of a
plant to grow with the force of
gravity and into the soil.
Gravitropism
and
phototropism
work
together, and
are controlled
by the
hormone
auxin.
Thigmotropism- a plant can be
effected by touch in many ways:
• Plants touched regularly could have
stunted growth
http://www.youtube.com/w
atch?v=H9MV5CgPgIQ&f
eature=fvsr
• Vines and climbing plants form
structures that attach themselves to
things they touch.
Ex. Some climbing plants have long,
twisting leaf tips, or petioles that wrap
tightly around small objects.
Ex. Other plants have extra growths
called tendrils that emerge near the
base of the leaf and wrap tightly
around any object.
http://www.youtube.com/watch?v=9bRtll-Ha0o
http://www.youtube.com/watch?v=dTljaIVseTc
http://player.discoveryeducation.com/index.cfm?guidAssetId=CCF5235B-94BB-42F18E4B-78F82E6847BB&blnFromSearch=1&productcode=US (life venus fly)
Tendrils