To find out how different factors (which will include light intensity and temperature) effect the rate of photosynthesis in Elodea (Canadian Pond Weed)

Photosynthesis Experiment

Aim

Introduction

Photosynthesis is a process used by plants to create food for energy. It uses light energy from the sun; the chlorophyll (which are green pigments) absorbs this into the leaves and uses it for photosynthesis. Oxygen is a product of photosynthesis. Because the leaves have a large surface area, they’re the cells that are specialized for absorbing CO 2 and light.

Prediction

I think that light, water, temperature and carbon dioxide are the factors that effect photosynthesis. The distance of the light or the intensity of it will effect the results. The closer the light is, the rate of photosynthesis will increase because the light will be closer and more concentrated due to the fact that it will not be over such a large surface area (less of the light will escape from the leaf). I think the rate of photosynthesis will be at its maximum when the temperature is between 25oC and 30oC because the photosynthesis needs heat to work but the pigments would get destroyed if you go over a certain temperature (45oC) and I think that is a suitable temperature. I also think that as CO2 increases the rate of photosynthesis will also increase, just because plants need CO2 to photosynthesize. I did mention water but as Elodea is grow in a pond that will not be a factor.

Apparatus

Elodea
Funnel
Measuring Cylinder
Water
Lamp
Ruler
Large Beaker

Safety

Make sure lamp is safe distance from water, so that if the water spills, it will not mix with the electricity, because it would cause an electric shock.
Tie long hair back so that it doesn’t get in the way of your eyes and so it doesn’t get damaged by the experiment.

Fair Test

I am going to make it a fair test by only changing one factor at a time and keeping the other ones the same. I will ...

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Apparatus

Elodea
Funnel
Measuring Cylinder
Water
Lamp
Ruler
Large Beaker

Safety

Make sure lamp is safe distance from water, so that if the water spills, it will not mix with the electricity, because it would cause an electric shock.
Tie long hair back so that it doesn’t get in the way of your eyes and so it doesn’t get damaged by the experiment.

Fair Test

I am going to make it a fair test by only changing one factor at a time and keeping the other ones the same. I will first change the temperature, starting at 15oC and ending at 25oC and then change the other factors and the temperature will be kept at the temperature that made the largest amount of gas from photosynthesis. I’m going to repeat the test two times to get an average of the results that I get, so that it is fairer.

Method

I will pour some water into a large beaker and I will get some Elodea and put it into the water. I shall then get a funnel, and place it over the Elodea, so that it will funnel the gas up the measuring cylinder. I would also need a lamp and a ruler, to measure the distance away that the lamp is from the Elodea. During the test I will move it either towards or further away from the Elodea. We will then measure the temperature and wait for the plant to photosynthesize.

Analysis

My evidence shows that the closer the light is to the Elodea it will increase the rate of photosynthesis, where as the CO2 and the temperature has a certain point which will put the rate of photosynthesis at its peak.

My results prove my prediction both right and wrong. I was right in saying that if you increase the light the rate of photosynthesis will increase. But I got the temperature that I thought it would make the plant photosynthesize at its peak wrong (the plant’s rate of photosynthesis was highest at 21oC) and the CO2 only increased the rate till a certain point, and after that point it stayed the same (around 2.0 – 2.5)

The greatest amount of gas produced was 72cm2. This gas was produced because the Elodea had too much oxygen that it didn’t need, so it gets rid of most of it, so it can use the space to bring in CO2. It lets out oxygen from the stomata (leaf pores) which are located at the bottom of the leaf cell.

Evaluation

Our experiment went quite smoothly, the only problem was with people mucking around. There are no results that don’t fit except the results at the bottom of my result table; they seem to jump up and down from 71 to 72 and back again. This could be down to bad readings though. I don’t really know how I could improve this experiment. I suppose if you used more precise measurements. E.g. NaHCO3 could have been done to two or three decimal places. If I were to do the same experiment with another factor to be involved, it would probably the type of water the plant is in, to see if salt water will affect the results in any way. I could have also used a different method, which would involve a gas syringe. I would pour some water into a large beaker and then use a gas syringe to measure the amount of CO2 in the water. I would then get some Elodea and put it into the water and place a lamp a certain distance away and during the test I would move it either closer or further away from the Elodea. I would then measure the temperature and wait for the plant to photosynthesize.