Green plants absorb light energy
using chlorophyll in their leaves.
They use it to react carbon dioxide
with water to make a sugar called
glucose. The glucose is used in
respiration, or converted into starch
and stored. Oxygen is produced as
a by-product.
Factors
Temperature
If it gets too cold, the rate
of photosynthesis will
decrease. Plants cannot
photosynthesise if it gets
too hot.
Carbon Dioxide Concentration
Sometimes photosynthesis is
limited by the concentration of
carbon dioxide in the air. Even if
there is plenty of light, a plant
cannot photosynthesise if there
is insufficient carbon dioxide.
Light Intensity
Without enough light, a plant cannot
photosynthesise very quickly, even if
there is plenty of water and carbon
dioxide. Increasing the light intensity will
boost the speed of photosynthesis.
Process
~ Light energy is absorbed by chlorophyll,
a green substance found in chloroplasts in
some plant cells and algae ~ Absorbed light
energy is used to convert carbon dioxide
(from the air) and water (from the soil) into
a sugar called glucose ~ Oxygen is
released as a by-product.
Equation (to right)
Some glucose is used for respiration,
while some is converted into insoluble
starch for storage. The stored starch can
later be turned back into glucose and used
in respiration.
Storage & Use Of Glucose
Storage
Glucose is needed by cells for respiration.
However, it is not produced at night when it is
too dark for photosynthesis to happen. Plants
and algae store glucose as insoluble products.
These include: Starch Fats and oils.
Use
Some glucose is used for respiration to
release energy. Some is used to produce:
Cellulose - which strengthens the cell wall
Proteins - such as enzymes and chlorophyll.
Plants also need nitrates to make proteins.
These are absorbed from the soil as nitrate
ions.