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Now I really screwed up. I sent off four samples to the University of Utah for carbon isotope analyses. They sent me back the four carbon isotope ratio values shown below:

sample 1 -29.1 per mil
sample 2 -25.8 per mil
sample 3 -16.2 per mil
sample 4 -15.9 per mil

I am like totally embarrassed. I know that the samples consisted of either amaranth or wheat. Two of the samples were from leaves grown under well-watered conditions and 2 were from leaves grown under limited-water conditions. Now, if I can get a few minutes I am sure that it will be easy to figure out which is which. But even after I do that, how am I going to know how the ci/ca ratios changed in wheat in response to the water when all that I now know is that the atmospheric CO2 had a value of -8 per mil?

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