Relative Quantification of Phloem Loading with ¹³CO₂ in Grass Leaves

A central challenge in plant physiology research is tracking the movement of photoassimilates, especially following their allocation via the phloem. To obtain better insight into movement of photoassimilates, we present a stable isotope-based approach to measure photoassimilate export from leaves. In this simple procedure, ¹³CO₂ pulse label is supplied to whole leaves or defined sections of the leaves, sugars are extracted at two timepoints and the reduction of ¹³C -signal quantified. The method uses the stable ¹³C isotope of carbon, is safe to use, and has been successfully applied in both monocot and dicot species.