Natriuretic peptides and cGMP modulate K⁺, Na⁺, and H⁺ fluxes in Zea mays roots

Recent evidence suggests that in plants, as in vertebrates, natriuretic peptides (NPs) regulate homeostasis. In this study noninvasive ion-selective vibrating microelectrodes were used to measure net fluxes of K⁺, Na⁺, and H⁺ in Zea mays root conductive tissue. Immunoreactant plant natriuretic peptides (irPNP) cause immediate net H⁺ influx and delayed net K⁺ and Na⁺ uptake. Delayed net K⁺ influx was also observed in response to 8-Br-cGMP, however, not accompanied by significant changes in net H⁺ fluxes. Furthermore, 8-Br-cGMP does not stimulate the plasma membrane H⁺-ATPase implying that cGMP directly affects cation channels. The data are consistent with NP and cGMP-dependent stimulation of nonselective cation channels with P_K > P_Na and point to a complex role for NPs in plant homeostasis.