Inhibition of the amino-acid co-transport carrier of Lemna gibba by incorporation ofp-fluorophenylalanine

In Lemna gibba L. a 2 h pretreatment with the amino-acid analogue p -fluorophenylalanine p -FPA inhibited subsequent uptake of L-alanine and reduced the transient depolarization of the plasmalemma caused by L-alanine. Uptake of 3–0-methylglucose was less affected. There was no effect of p -fluorophenylalanine on the resting potential or on the fusicoccin- or light-dependent hyperpolarization of the cells. Furthermore, fusicoccin-stimulation of uptake of L-alanine and 3–0-methylglucose was also unaffected. The results suggest that p -FPA pretreatment selectively acts on the H⁺-amino-acid co-transport carrier, that the H⁺-hexose co-transport carrier is much less affected, and that the proton pump appears to be unaffected by p-FPA.