PAG 12.3: Investigating the rate of oxygen production in pondweed
Introduction:
In this practical, we investigated the rate of oxygen production in pondweed,
using it as a model for photosynthetic organisms. Photosynthesis is a process
where light energy is converted into chemical energy and produces oxygen as a
by-product. The number of bubbles counted in each experiment can be used to
indirectly measure the rate of photosynthesis. The limiting factors of
photosynthesis include CO2 concentration, light intensity, and temperature
(Fielding and Anderson, 2018, p.180). In the experiment, we changed the
concentration of carbon dioxide (CO2) by using different amounts of bicarbonate
of soda to water. By changing the concentration of CO 2, we can investigate its
effect on the rate of oxygen production and, therefore, rate of photosynthesis.
Aim:
The aim of this experiment is to investigate the effect of varying CO 2
concentrations on the rate of oxygen production in pondweed. We aim to
determine how CO2 availability influences the photosynthetic rate in an aquatic
environment. This will show us the relationship between CO 2 concentration and
photosynthesis in plants.
Hypothesis:
Our hypothesis is that increasing the concentration of CO 2 will lead to an
increase in the rate of oxygen production, as CO 2 is a substrate required for the
Calvin cycle in photosynthesis. The oxygen produced will be measured by
counting the air bubbles produced by the pondweed over a fixed period to
determine the link between CO2 concentration and the rate of photosynthesis. By
altering CO₂ concentration, we can study its impact on the photosynthesis rate in
pondweed, with the hypothesis that increased CO₂ concentration will lead to
higher rates of oxygen production.
Procedure:
1. Cut a 10cm length of pondweed and remove a few leaves from the stem to
expose the cut surface.
2. Fill a boiling tube with 40cm3 of the correct concentration of NaHCO3
dissolved in water.
3. Add the pondweed in the boiling tube and cut the stem underwater to
avoid an air lock.
4. Position the boiling tube in a test tube rack and set up a lamp 30cm away
from the boiling tube.
5. Ensure the temperature stays constant throughout the experiment (a
water bath set to 20-25°c would keep this variable constant).
6. Allow the pondweed to acclimatise for 2 minutes.
7. Count the number of bubbles produced in 3 minutes and record the
number in an appropriate table.
8. After each trial, remove the pondweed and place it in a new concentration
of NaHCO3, and repeat.
Introduction:
In this practical, we investigated the rate of oxygen production in pondweed,
using it as a model for photosynthetic organisms. Photosynthesis is a process
where light energy is converted into chemical energy and produces oxygen as a
by-product. The number of bubbles counted in each experiment can be used to
indirectly measure the rate of photosynthesis. The limiting factors of
photosynthesis include CO2 concentration, light intensity, and temperature
(Fielding and Anderson, 2018, p.180). In the experiment, we changed the
concentration of carbon dioxide (CO2) by using different amounts of bicarbonate
of soda to water. By changing the concentration of CO 2, we can investigate its
effect on the rate of oxygen production and, therefore, rate of photosynthesis.
Aim:
The aim of this experiment is to investigate the effect of varying CO 2
concentrations on the rate of oxygen production in pondweed. We aim to
determine how CO2 availability influences the photosynthetic rate in an aquatic
environment. This will show us the relationship between CO 2 concentration and
photosynthesis in plants.
Hypothesis:
Our hypothesis is that increasing the concentration of CO 2 will lead to an
increase in the rate of oxygen production, as CO 2 is a substrate required for the
Calvin cycle in photosynthesis. The oxygen produced will be measured by
counting the air bubbles produced by the pondweed over a fixed period to
determine the link between CO2 concentration and the rate of photosynthesis. By
altering CO₂ concentration, we can study its impact on the photosynthesis rate in
pondweed, with the hypothesis that increased CO₂ concentration will lead to
higher rates of oxygen production.
Procedure:
1. Cut a 10cm length of pondweed and remove a few leaves from the stem to
expose the cut surface.
2. Fill a boiling tube with 40cm3 of the correct concentration of NaHCO3
dissolved in water.
3. Add the pondweed in the boiling tube and cut the stem underwater to
avoid an air lock.
4. Position the boiling tube in a test tube rack and set up a lamp 30cm away
from the boiling tube.
5. Ensure the temperature stays constant throughout the experiment (a
water bath set to 20-25°c would keep this variable constant).
6. Allow the pondweed to acclimatise for 2 minutes.
7. Count the number of bubbles produced in 3 minutes and record the
number in an appropriate table.
8. After each trial, remove the pondweed and place it in a new concentration
of NaHCO3, and repeat.
