Help: Excel graphing/trendlines - leaf transpiration

Hey guys,

This is my first post. Looks like a great site, good to have this kind of forum.

I've mentally hit a brick wall or some such thing, in that I'm gradually putting together the shattered pieces. I have an excel data set for a leaf transpiration experiment which I'm manipulating the graphs and trying to get an understanding of the full story from the visual data in the graphs. Basically, its not talking to me at any great lengths and I want to be able to infer the information I believe exists in the results for incorporation into the discussion and then conclusion.

There are some variables that I'm not sure whether excel is capable of ruling out or whether it can assist me in determining errors in my technique, so perhaps this is why I'm not seeing the full picture in my data or I'm creatign the wrong style graphs. I've completed other experiments where my data was really clear and easy to interpret, therefore I'm thinking it is merely an incorrect method/style/technique I'm using for my graphs.

See my excel spreadsheets below

https://docs.google.com/open?id=0BzXT6JUPPBVyOWMzYWZkODgtMjE0ZC00MzI1LWIxNGEtMWQxOGFkZWUzNGNl

Overview of experiment (not necessarily important, but give you idea of what excel data represents):

• two seperate branches with leaves from two different species were used in this practical. Each species was cut within 15 minutes of being successfully inserted into the potometer, which involves cutting the sample a second time under water immediately prior to sticking into the tubing on the potometer (which also had to be underwater).
• Then I added a coat hanger to the potometer for support, which took several more minutes.
• The water level was set to 0cm once I was ready to start and the plant was not touched until the end of each 45 minute segment (x 7, but I am only going to include the first 6 in my report).
• There were occassional delays of several minutes between each 45 minute segment, to allow for the water level to be reset to 0 cm and any issues to be corrected before continuing prac (i.e. coat hanger support problem; taking outside and setting up; placing bag over plant; waiting until the time was at a five minute interval; or just setting up the heater).
• It involved one potometer (used for measuring the transpiration rate of leaves), therefore only one experiment could be undertaken at a time.
• Although I didn't need to record the temperature, I did for one species (muttonwood, with a digital thermometer); but not the other (Acacia). Short version, I was getting sick of repeating the experiment due to technical difficulties and only used a fowles vacola preserving thermometer for the Acacia, which didn't change temperature fast enough. Meaning 2 seperate prac fails, wasting 360 minutes of my time.
• The potometer transpiration rate was for 5 minute intervals and recorded in excel.
• Leaves from each species used in the prac were cut from the branch following the experiment and stuck to paper then photocopied. From this I was able to cut out the leaves and determine surface area with further calculations.
• One leaf fell off the muttonwood when I was trying to set up outside and the potometer needed to be placed on the ground under the shrub instead of sitting on the branch in the shrub.

I can see by my graphs in excel that the muttonwood and acacia plants transpired most during the first 45 minutes of the practical in the control, however I'm not sure what is happening to the water turgor in the plant in the time after the branch is cut and upto when it is successfully inserted into the potometer.