| Abstract: | The tetraammonium salt of the K+ binding fluorescent dye benzofuranisophthalate (PBFI) was used to investigate the influence ofpotassium nutrition (0.1–2.1 mol m–3) on apoplasticK+ inVicia faba leaves by means of ratio imaging. As a referencethe infiltration-centrifugation method was used. Both methodsreflected the influence of K+ supply on apoplastic K+ concentration.The abaxial leaf side revealed significantly higher K+ concentrations(20-25 mol m–3) than the adaxial side (5–8 mol m–3).Application of CCCP led to an immediate increase in apoplasticK+ demonstrating the reliability of the PBFI method. Key words: Vicia faba, leaf, apoplast, K+, PBFI, ratio imaging, ratiometric fluorescence microscopy |
