ABSTRACT
The oxygen isotopic composition of plant organic matter and the CO2, O2 and water vapour exchanged between the plants and the atmosphere are imprinted with the oxygen (O) signature of leaf water. This is a useful signal because the O content of leaf water is unique and is influenced by environmental conditions. Water is taken up by the roots and transported with relatively little isotopic modification to the leaves. In leaves, water is lost to the atmosphere in the process of evapotranspiration, coupled with the leaf CO2 and O2 exchange. Any isotopic enrichment occuring in leaf water is superimposed on the background isotopic signature of the input water. During evaporation from the leaves, there is an isotopic interaction between the liquid and the vapour phases. To check for the effects of decreasing leaf water volume during the day, a separate box model was employed.
