Viewpoint: Signalling by potassium: another second messenger to add to the list?

Potassium (K+) retention in the roots and shoots is correlated with increased tolerance to salinity and drought. However, in response to salt stress, K+ efflux  from roots is induced. Shabala investigates three possible reasons for this stress-induced K+ efflux: K+ could leave to charge-balance the Na+ that enters, K+ efflux could trigger programmed cell death for example in the promotion of aerenchyma, and K+ efflux could serve as a metabolic signal that slows growth and elicits defense responses. He provides a scenario through which this latter effect could occur, and suggests that by analogy to transient Ca2+ fluxes, we might start thinking about transient cytosolic K+ fluxes as signals. J. Exp. Bot. 10.1093/jxb/erx238