Extracting relevant physiological information from polar auxin transport data in Panax ginseng

Background: Measuring polar auxin transport (PAT) in plants and drawing conclusions from the observed transport data is only meaningful if these data are being analysed with a mathematical model which describes PAT. In this report we studied the polar auxin transport in Panax ginseng stems of different age and grown on different substrates. Methods: We measured polar IAA transport in stems using a radio labelled IAA and analysed the transport data with a mathematical model we developed for Arabidopsis. Results: We found that PAT in ginseng stems, as compared to Arabidopsis inflorescence stems, has a 2-fold lower transport velocity and a 3-fold lower steady state auxin flux. Conclusion: We were able to pinpoint two physiological parameters that influenced the observed transport characteristics in ginseng which differ from Arabidopsis, namely an increase in immobilization together with a reduced reflux of IAA from the surrounding tissue back to the transporting cells.