Respirometer Experiment

RESEARCH QUESTION

Which one has a higher rate or respiration between dicotyledonous (peas) and monocotyledonous (maize) seeds and what is the effect of temperatures (room temperature, 40, 60) on the rate of respiration as determined by oxygen usage estimated with a respirometer?

AIM

The aim of this experiment is to investigate which seed has a higher rate of respiration and how different temperatures (room temperature, 400C, 600C) affects the rate of respiration of dried, fresh and germinating monocotyledonous (peas) and dicotyledonous (maize) seeds. This will be done using a respirometer which will measure the rate of oxygen usage. The change in volume recorded by the respirometer pipette will be an indication of this.

BACKGROUND INFORMATION

Part I
Assembly of respirometers:
1. A total of 4 respirometers were set up. The respirometers are numbered 1, 2, 3 and 4.
2. Germinating seeds are placed in Respirometer 1, fresh seeds and beads are in Respirometer 2, dry seeds and beads in respirometer 3 and beads alone are placed in Respirometer 4.
3. A typical respirometer was set up as follows:
• A vial fitted with a stopper with a hole was taken.
• A pipette was taken and inserted through the stopper so that it’s wide end is in the vial.
• A wad of cotton soaked in 15% KOH is placed in the vial. A layer of dry cotton is placed over the cotton wad so that the KOH does not come in contact with the seeds.
• The samples (germinating seeds or fresh seeds and beads or dry seeds and beads or beads alone) are placed over this dry cotton layer.

Fig: Assembling a respirometer
(http://www.phschool.com/science/biology_place/labbench/lab5/assemble.html)

Part 2
This was done as per the method of

Germinating peas and maize respire at faster rates than fresh and dried peas and maize at room temperature and 400C(graph no). This could be because pea seeds have two cotyledons as compared to the single one of maize so oxygen usage is also more. These results support my hypothesis stated earlier. Respiration is an enzymatic process where enzymes are required at every step in the breakdown of glucose. At 600C for both peas and maize the respiration rate went down as the enzymes denatured. This suggests that as the temperature increased cellular respiration increased until it reached an optimal level somewhere between 400C to 600C. (Text book ref)

BIOLOGICAL UNCERTAINITIES

I bought the seeds two days before the experiment attempting to purchase seeds of the same age with almost identical sizes. However, even though I attempted to control the biological factors, some seeds germinated faster and at a better rate than others. The seeds that germinated better would also consequently give a higher rate of cellular respiration than the rest. I tried to correct this by choosing germinated seeds of almost similar visible size and also added in each respirometer the amount of dry/fresh seeds and beads that would equal to the total volume of germinating seeds and water in a graduated