Biology Lab Report Template: Temperature and Photosynthesis

This is a biology lab report template written in international baccalaureate curriculum. This biology lab report template gives the main headings that students should use in their lab reports. The lab report investigates how temperature affects the rate of photosynthesis of a leaf.

Subject

How Does Temperature Affect The Rate Of Photosynthsis Of A Mauna Loa Supreme Leaf

Aspect 1: Defining the problem and selecting the variables.

Background Information:

Temperature is one of the factors that affect the rate of photosynthesis of a plant. The rate of photosynthesis in relation to temperature forms a bell curve.
At low temperatures the enzymes responsibility for photosynthesis have very little energy so the rate of photosynthesis is very slow. If it is cold enough for water to freeze it can be very harmful to a plant.
As the temperature increases, the enzymes get more energy so the rate of photosynthesis increases.
If it gets too hot the enzymes begin to lose their shape (denature). This means they are unable to function properly and the rate of photosynthesis decreases again. Also, at higher temperatures the stomata close to prevent water loss. This also stops gas exchange which slows photosynthesis even further. If it is hot enough for water to boil this can be very harmful.¹

Products of photosynthesis are Oxygen gas, water and glucose. In this experiment, the amount of oxygen is going to be considered to decide on the rate of photosynthesis.

6CO₂ + 12H₂O à C₆H₁₂O₆ + 6O₂ + 6H₂O

Equation 1: Reaction equation of photosynthesis.

Aim:

To investigate the effect of temperature on the rate of photosynthesis of  a Mauna Loa Supreme leaf.

Research Question

How does temperature affect the rate of photosynthesis of Mauna Loa Supreme leaf where the light intensity, CO₂ concentration of the environment, size and species of the leaves used in each trial and amount of water (100 ml in each trial) used for the water bath is kept constant.

Variables:

Independent Variables:

• Temperature of the water in the water bath in which the plant runs the photosynthesis reaction. The temperatures, which are measured by using thermometer, of water in the water bath is going to be 10⁰C ,20⁰C ,30⁰C,40⁰C and 50⁰C.

Dependent Variables:

• The rate of photosynthesis of Mauna Loa Supreme leaf. The evidence for the rate of photosynthesis will be understood by measuring the Oxygen gas given off as a result of photosynthesis by using vernier oxygen sensor.

Controlled Variables:

• CO₂ concentration of the environment.
• Amount of water, which is going to be the reaction medium, in the water bath.
• Species of the plant, from which the leaf that is going to be used for the photosynthesis reaction is taken and which is Mauna Loa Supreme.
• Size of Mauna Loa Supreme leaf.

Aspect 2: Controlling the variables

As mentioned in Equation 1, photosynthesis requires CO₂ so the more CO₂  in the environment, the greater rate photosynthesis occurs. Thus the concentration of CO₂ in the environment should be kept constant and it is going to be done so as the experiment is carried in the same environment.

The temperature change is provided by water bath. The amount of water in the water bath in the water bath should be kepth constant for each temperature sample. This because of that; two different amounts of water can give different energies to the environment even the two different amounts of water have the same temperature. As the amount of water increases, its ability to warm up the environment increases too, so the amount of water should be kept constant. In this experiment, the amount of water is 100 ml (±0,5 ml) for each sample temperature.

First controlled variable is species of the plant from which the leaf is taken. Every plant has different properties for carriyng on photosynthesis like the number of stomas on the leaves or the thickness of cuticle of the leaves and etc. As a result of all these, some plants can carry on photosynthesis with a greater rate than some other plants even if they are in the same conditions. So it is important to take the leaves from the same species of plant, which is Mauna Loa Supreme.

Even if the leaves are taken from the same plant, Mauna Loa Supreme, a leaf from Mauna Loa Supreme can carry on photosynthesis with a greater or lower rate than a leaf again from Mauna Loa Supreme, in the same conditions. This is a result of the differences between the size difference between the two leaves, because the two leaves from the same plant can have different number of stomas, which directly affects the rate of photosynthesis so the leaves should be same size and mass. It is very hard to find leaves with the same size and mass so while conducting the experiment, the leaves with sizes and masses that are close to each other should be chosen.

Aspect 3: Developing a method for collection of data

Materials:

• Mauna Loa Supreme leaves with same size and mass.
• Vernier Oxygen Sensor
• Thermometer
• Glass erlenmayer flask
• Graduated cylinder of 100ml(±0,5ml )
• Kettle
• Laptop
• Cutter
• Balance
• refrigerator

Method

1. Cut 6 leaves of same size and mass from Mauna Loa Supreme. Measure their mass by using Balance.
2. Put each leaf in an erlenmayer flask.

For the sample temperature of 10⁰C,

• Place the vernier oxygen sensor on one of the erlenmayer flasks and cover the gabs between the vernier oxygen sensor and the flask with parafilm to prevent the loss of oxygen gas.
• Connect the vernier oxygen sensor to your laptop and get the Logger Pro software ready on your laptop.
• Measure 100ml of tap water with graduated cylinder. Measure its temperature. Its temperature will be more than 10⁰C so cool it down by using a refrigerator.
• As you measure the temperature of water as 10⁰C immediately poor it into the water bath.
• Place the erlenmayer flash with the leaf in it and the oxygen probe placed on it in the water bath.
• Start the Logger Pro software to start collecting your data.
• Repeat the same steps for the other 4 samples.
• Be careful with that; if you need to heat the tap water to get the expected temperature for the sample, don’t heat water after measuring the amount of water because water evaporates as you heat it up and some water leaves the kettle as a gas. Before measuring the amount of water, heat plenty of water and after heating measure its temperature.
• After heating, if its temperature is higher than the expected value measure 100ml of water with a graduated cylinder and let it cool down in the graduated cylinder. While it is cooling down, place the thermometer in water and as soon as you get the expected value, pour the 100ml(±0,5ml ) of water in the water bath.
• After heating, if the temperature of water is lower than the  expected value, heat it more and repeat the steps in 10-b.

After collecting data with at least doing 3 trials for each sample, to get more accurate results, by using Microsoft Office Excel, the average values of the trials for each sample should be calculated. After calculating, percentage uncertanities should be found and the graph of concentration of oxygen gas vs. temperature should be drawn. While drawing the graph, error bars should be added to the graph. After all, a conclusion ought to be come and some alternative solutions for the weak points of the method should be found, to increase the accuracy of the data.

After finishing the experiment, while cleaning up the laboratory, the leaves used in the experiment should not be put into rubbish bin, being avare of that they are still alive.

References

1. WikiAnswers,(2011). How does temperature  affect the  rate of photosynthesis? Retrieved on 04.11.2012, from; http://uk.answers.yahoo.com/question/index?qid=20100320075641AA8rDq1