PHOTOSYNTHESIS is the fundamental process by which plants manufacture carbohydrates
from raw materials using energy from light.
Chlorophyll traps light energy and converts it into chemical energy for the formation of
carbohydrates and their subsequent storage.
Photosynthesis reaction:
light
Carbon dioxide + water ---------------> glucose + oxygen
chlorophyll
6CO2
+ 6H2O -----------------> C6H12O6 + 6O2
4 things are required for photosynthesis to take place:
1. H2O — needed to make glucose (photolysis splits H2O into O and H)
2. Light— energy
3. CO2 — air – needed to make glucose
4. Chlorophyll — an enzyme which facilitates (makes possible) photosynthesis.
Plants take carbon dioxide in through the stomata in the leaves.
Plants take in water through the roots.
Factors that affect photosynthesis:
CO2
Light
Temperature
(30o is the
temperature at which
chlorophyll operates
the best. At 40o it can
denature).
PHOTOTROPISM = response to light
Auxin is a growth hormone in plants. It is moved from growth centres (aka meristems) to
shadier parts of the plant where it promotes growth. In the light areas auxin is denatured to
inhibit growth. Therefore, the plant grows more on the darker side, making the plant grow
towards the light.
CUTICLE
XYLEM
protection
transport H2O
from roots
PHLOEM
transports
products of
photosynthesis
away from leaf
e.g. to bulb
STOMATA for gas exchange
i.e. CO2 in, O2
out
GUARD
to open or close
CELLS
the stomata