Plant Photosynthesis Unit
Leaf anatomy
Photosynthesis
• Is a chemical reaction – a rearrangement
of the atoms of a substance.
• It is the most important chemical reaction
on the planet
What is the chemical reaction
of Photosynthesis?
Carbon Dioxide + Water  Glucose + Oxygen
6CO2 + 6H2O  C6H12O6 + 6O2
Description of Photosynthesis
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The process of changing light energy to chemical energy
Energy stored as sugar
Occurs in plants and algae
Plants need light energy, CO2, and H2O
Takes place in the chloroplast using chlorophyll the green
pigment in plants
Energy flow of photosynthesis
Light
Energy
CO2
Oxygen
H2O
CO2
H2O
Leaf Anatomy
• Whole leaf looks green to
us but most of the cells &
cell materials are colorless
or clear
• The green color comes
from the chlorophyll
molecules in the
chloroplast
Leaf Section
• On top and bottom are the
cuticle layer and epidermis
cells
• In the middle are the
mesophyll cells where
chloroplasts are. This is
where photosynthesis
happens.
• Air spaces are where gas
exchange occurs
• On bottom only in most plants
are the stoma which let CO2
and O2 out
Mesophyll Cells
• Where photosynthesis
occurs, are in the
mesophyll cells.
• two kinds:
– palisade
parenchyma : Packed
close together. Where
most photosynthesis is
done.
– spongy parenchyma:
Cells aren't so close.
There are roomy air
spaces between them.
Chloroplast
• Inside the stoma and the
grana, is where
photosynthesis happens.
• Have their own genetic
material to make more of
themselves.
• Each is a little carbohydrate
factory, powered by solar
energy, and for which the
only raw materials are
carbon dioxide, water, and a
few minerals.
Inside the
Chloroplast
• The little round flat pillow or
pancake shaped things are
called thylakoids. A stack of
them is called a granum.
• There can be from 2 to
around 100 thylakoids in one
granum.
Thylakoid
• Chlorphylls and other
pigments that start the
process are here on the
outer layer.
• Photons from sunlight hit
the pigments, electrons are
"knocked" loose, and off
they go to energize the
complicated process of
photosynthesis.