Simulating Real Plant Growth

This is the final paper and it needs to demonstrate all that I have learned over the past 4 months.
Here it goes:
Assuming that plant grows in 8 steps at the 0.45 rate and that the first stem lenght is 20mm - This is what I have so far:
1/ I made a table showing the length of the plant's stem at the end of each step.
2/ I made a graph of the values in the table
3/ I, of course, wrote a formula representing the growth for each step:
new length=old lenght + 0.45xold length

Ok. Here is the problem:
What else could I do with this data?  What other relationships could I determine between the steps?  

Remember, I need to demonstrate knowledge through using a spreadsheet and performing analysis with a purpose.

Please throw some ideas at me and make me impress my teacher!!!!!
THX