Figure 1

HPLC traces of potato leaf exudates. The terminal leaflets of potato leaves were excised from glasshouse plants, petioles were re-cut under water and the freshly cut end transferred to 200 μl 5 mM CaCl₂ (trace A) or 200 μl 15 mM EDTA (trace B). Samples were transferred to a saturated atmosphere to exude in the dark for 90 min. The exudation medium was brought to 5% MPA, 5 mM TCEP, centrifuged and injected onto a Coregel 64H column. Traces were recorded at 245 nm using a diode array detector and insets show the absorbance spectra of the peaks at 12.2 min. Trace C was authentic AsA (2.27 nmol) which gave a peak height of 42 mAU. The unbound peak at 6.3 min contained MPA.