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 PK > PNa and point to a complex role for NPs in plant homeostasis. © 1999 Academic Press.