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Plant Kingdom
Mincer/Scully
What Is A Plant?
• Multicellular, eukaryotic, cell walls
made of cellulose, and carry out
photosynthesis in structures called
chloroplasts using a pigment called
chlorophyll.
What a Plant Wants…What a
Plant Needs…
• Sunlight-Plant harness the energy of
the sun to make food. This process is
called photosynthesis.
• Gas Exchange- Plant cells need both
oxygen AND carbon dioxide, since
plants do both photosynthesis and
cellular respiration.
What A Plant Needs
• Water and Minerals- All cells, not just
plant cells, need a constant water
supply. Also, plant cells may get their
food from photosynthesis, but there are
other elements that they need to make
certain structures.
• Movement of Water and MineralsPlants get water and minerals from their
roots. They need to be able to move
each of these to the rest of the plant
tissues.
The Life Span of Plants
• Annuals: Live for only one year
• Biennial: Live for two years
• Perennial: Live for many years
Plants through Geologic
History
• Plants are thought to have evolved
from a green algae ancestor.
• Mosses  Ferns  Conifers 
Flowering plants
Vascular Tissue
• There are two types of vascular tissue.
• Xylem- Carries water
• Phloem- Carries phood. (food)
Gymnosperms
• Gymnosperms are plants that bear
cones instead of fruit. Often called
conifers. These are vascular.
• Many gymnosperms are evergreens,
which means that they do not lose
their leaves during the cold season.
Angiosperms
• Angiosperms are flowering plants.
They bear fruit. There are two kinds
of angiosperms:
– Monocot- 1 seed leaf in the fruit
– Dicot- 2 seed leaves in the fruit
Monocot vs. Dicot
Plant Structure
• There are three basic structures for most
plants:
• Leaf- Food organs for plants, where
photosynthesis takes place as well as gas
exchange.
• Stem- Holds the leaves upright, and
provides a conduit between the leaves and
the roots
• Root- Anchor for the plant; also gathers
water and minerals from the soil
Structure of a Leaf
• Each leaf has several layers. Each layer
has a specific function.
• Cuticle- Waxy NON CELLULAR layer on
the top of the leaf. Keeps water from
evaporating out of the leaf.
• Upper Epidermis- Directly under the
cuticle is a clear layer of tough cells.
These cells help protect the leaf from
damage. There is another layer found at
the bottom of the leaf
Structure of a Leaf…
• Palisades mesophyll- This layer has very
green, elongated cells. This is where most
of the photosynthesis happens in a leaf.
These cells are darker green because they
are packed with chloroplasts
• Spongy mesophyll- This layer has air
pockets which connect with openings in
the bottom of the leaf. This is the main
way that gas exchange happens in plants.
Leaf Structure
Leaf Structure
• Lower Epidermis- This layer is similar to
the upper epidermis, but it has stoma, or
holes flanked by guard cells through which
gases are exchanged with the atmosphere
• Guard Cells- These are specialized cells
which can close when a plant is losing too
much water vapor through its leaves.
Chloroplasts
• Chloroplasts are tiny
organelles which contain
chlorophyll, or the pigments
which enable the plant to do
photosynthesis.
• There are two parts to a
chloroplast:
– Stroma: The open space inside
a chloroplast
– Thylakoid stacks: The
membrane bound stacks inside
a chloroplast.
Guard Cells
• Guard Cells are specialized cells
which flank the stoma in the bottom
of the leaf.
• During times of low water (drought),
the guard cells will swell with extra
water and close, closing the stoma.
Photosynthesis
• CO2 + H2O  C6H12O6 + O2
• Of course, its more complicated than this!
• There are two parts to the photosynthesis
reaction:
– Light Dependent Reaction- Takes place in the
thlyakoid. Light photons strike H2O molecules and
(with a little help from chlorophyll), break them down.
ATP is created.
– Light Independent Reaction- Takes place in the
stroma. CO2 is broken down (with more help from
chlorophyll) and remade into C6H12O6 and O2
Photosynthesis
Light
Independent
Reactions
Happens
Second
Light
Dependent
Reactions
Happens First
Stems
• Stems do two things:
– Hold the Leaves up to the
sunlight
– Provide a way for food to
flow to the rest of the plants
from the leaves, and water
to flow from the roots to the
rest of the plants.
• Phloem- Tissue through
which PHOOD flows through
the plant
• Xylem- Tissue through which
WATER flows through the
plant
Roots
• Roots do two things:
– Anchor plants in the ground
– Absorb water and nutrients
• They do this by….you guessed
it, diffusion and osmosis!
• Water is kept continually
moving against the pull of
gravity by transpiration
occurring in the leaves.
• Transpiration is the process
by which the plant turns
liquid water into water vapor.
Plant Reproduction
• Plants can reproduce both sexually and
asexually.
• Plants reproduce asexually through:
– Spores- tiny balls of densely packed cells, not
all plants make them
– Rhizomes- also called runners, plants send
out an underground stem from which new,
genetically identical plant will form.
Sexual Reproduction in Plants
• Plants that sexually reproduce
produce seeds.
• Gymnosperms- These produce their
seeds in cones. Some cones are
very tough, to protect the seeds
• Angiosperms- These produce their
seeds by way of flowers. They
usually produce some kind of fruit.
Angiosperms
• Very young, evolutionarily speaking, the
first angiosperm ancestor appearing in the
fossil record about 125 million years ago.
(For plants, this is young)
• Angiosperms are thought to have
coevolved with certain species of insects,
who helped to pollinate the plants and
disperse the seeds.
Flowers
• Flowers are the sex
organs of plants.
• Many flowers have
both male and
female parts
• Flowers are
designed to attract
pollinators, i.e.
birds or insects
Plant Adaptations and
Responses
• Plants respond to their environment, like
animals, but use a different means to
respond.
• Plants use hormones to respond to their
environments
– A hormone is a chemical messenger (molecule)
that causes a change in its target cells
– The growth hormones in plants are called
auxins
Plant Responses
• Gravitropism- Plants will grow
so that their leaves point upward
and their roots downward in
respect to gravity.
• Thigmotropism- Some plants
can respond to touch. For
example, vines will wrap
themselves around objects that
they come into contact with.
Other Responses
• Phototropism- Plants will
bend toward the light. This
can take place over just a
few hours, or days
• Rapid Responses- Some
plants can respond quickly
to stimuli, e.g. the Venus fly
trap or the mimosa plant
Other Responses
• Seasonal Responses- Some
trees will shut down in the
winter time, and lose their
leaves. These are called
deciduous
• Chemical Defenses- Some
species of plant will deploy
chemical defenses when
attacked. Some are poisons;
some chemicals will actually
attract predators of the insects
that are feeding.