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