Phloem unloading in Arabidopsis roots

It is well known that long distance transport and movement of molecules is enabled by phloem, but the precise mechanism of loading/unloading of phloem mobile compounds is not known. In this article, Ross-Elliott et al. used a combination of approaches (non-invasive imaging, 3D-electron microscopy, and mathematical modelling) to explore phloem unloading. The authors show that unloading of solutes in Arabidopsis roots occurs through plasmodesmata by convective unloading, a combination of mass flow and diffusion. By contrast, unloading of small proteins occurs in pulses, which they describe as batch unloading, through specialized funnel plasmodesmata, into the phloem pole pericycle.  The authors also propose a new model of phloem unloading in Arabidopsis roots. (Summary by Mather Khan) eLife 10.7554/eLife.24125