Electrokinetic constraints on intercellular signalling in plants

Plant cells, though enclosed by rigid walls, remain interconnected through nanoscale, membrane-lined pores called plasmodesmata. A puzzling feature of chemical signalling through these nanopores is their preferential transport of negatively charged molecules. This charge selection is counterintuitive because plasmodesmal walls are negatively charged - which should favour the transport of positively charged species according to electrokinetic principles. One hypothesis attributes this apparent `inversion' to the presence of positively charged tether proteins within plasmodesmata. Here, we evaluate the influence of such positively charged obstructions along the transport path on the movement of signalling molecules using electrokinetic theory. We assess whether their presence can fully account for the observed permselective behaviour. Further, by linking nanoscale electrokinetic effects with tissue-scale transport dynamics, we explore the broader implications of this mechanism for long-range hormone signalling in plants.