How do environmental factors affect the
rate of photosynthesis?
Light intensity
The effect of light intensity
on the rate of photosynthesis.
Investigation of the effect of light
intensity on the rate of photosynthesis
Procedure:
1 Set up the apparatus
as shown. Keep the
temperature constant.
Turn on the lamp at a
distance of 0.1m and
allow the pond weed
to equilibrate for 5
minutes.
rubber tubing
dilute sodium
hydrogencarbonate
solution
clip
pipette
thermometer
water
bench lamp
Hydrilla
Investigation of the effect of light
intensity on the rate of photosynthesis
Procedure:
2 Suck up the
solution from the
boiling tube. Close
the clip
completely and
record the starting
position of the
meniscus in the
pipette.
rubber tubing
dilute sodium
hydrogencarbonate
solution
clip
pipette
thermometer
water
bench lamp
Hydrilla
Investigation of the effect of light
intensity on the rate of photosynthesis
Procedure:
3 After 5 minutes,
record the final
position of the
meniscus in the
pipette. Calculate
the rate of
photosynthesis.
Record two more
readings.
rubber tubing
dilute sodium
hydrogencarbonate
solution
clip
pipette
thermometer
water
bench lamp
Hydrilla
Investigation of the effect of light
intensity on the rate of photosynthesis
Procedure:
4 Repeat steps 1 to 3
with the bench
lamp placed at a
distance of 0.2m,
03m, 0.4m and
0.5m from the
apparatus.
rubber tubing
dilute sodium
hydrogencarbonate
solution
clip
pipette
thermometer
water
bench lamp
Hydrilla
How do environmental factors affect the
rate of photosynthesis?
rate of photosynthesis
Light intensity
light intensity
1) Initially, the rate of photosynthesis increases rapidly
with increasing light intensity as more energy is
supplied to the light reactions.
How do environmental factors affect the
rate of photosynthesis?
rate of photosynthesis
Light intensity
saturation point
(飽和點)
light intensity
2) The increase stops when the light intensity reaches a
saturation point.
How do environmental factors affect the
rate of photosynthesis?
rate of photosynthesis
Light intensity
rate limited by
other factors
saturation point
(飽和點)
light intensity
3) The rate is now limited by others factors,
e.g. CO2 concentration and temperature.
How do environmental factors affect the
rate of photosynthesis?
CO2 concentration
The effect of carbon dioxide
on the rate of photosynthesis.
How do internal factors of plant affect the
rate of photosynthesis?
1) mid-rib branches into a
network of veins
two layers of tissues:
palisade mesophyll
& spongy mesophyll
How do internal factors of plant affect the
rate of photosynthesis?
2) Palisade mesophyll
 made up of tightly
packed cylindershaped cells
 contain many
chloroplasts
How do internal factors of plant affect the
rate of photosynthesis?
3) Spongy mesophyll
 cells not regular
in shape
 fewer chloroplasts
 many air spaces
How do internal factors of plant affect the
rate of photosynthesis?
4) Epidermis
 cover both surfaces
 protects cells against
mechanical injuries
and infection
How do internal factors of plant affect the
rate of photosynthesis?
4)  Epidermal cells have
no chloroplasts,
except guard cells
How do internal factors of plant affect the
rate of photosynthesis?
5) Cuticle
 cover the epidermis
 reduces loss of water
How do internal factors of plant affect the
rate of photosynthesis?
6) Stoma
 surrounded by guard
cells which control
the opening and
closing of the stoma
 guard cells have
many chloroplasts
stoma
guard cell
How do internal factors of plant affect the
rate of photosynthesis?
6)  There are far fewer
stomata on the upper
surface of a leaf to
reduce water loss.
stoma
guard cell
How do internal factors of plant affect the
rate of photosynthesis?
7) Vascular bundles
 for transport
solutions containing
chemical which
plants need.
 contains xylem
and phloem
How do internal factors of plant affect the
rate of photosynthesis?
Xylem
 transports water and
minerals from the roots
to the leaves
Phloem
 transports nutrients
from the leaves