You have been hired by a farmers cooperative to investigate potential water stress in their crop. Without access to a fancy portable gas exchange analyzer or a fluorometer, you turn to stable isotope analysis. Explain how you would go about conducting this analysis and interpreting the data. Your answer should include the following points:

I) The tissue you will sample

II) What isotope you will use for the analysis

III) What you would expect to see if the crop is stressed - i.e. isotopic enrichment (higher isotopic values) or depletion (lower isotopic values)

IV) How this analysis would differ from measuring photosynthesis directly