Organolead Toxicity in Plants: Triethyl Lead (Et3Pb+) Acts as a Powerful Transmembrane CP/OH- Exchanger Dissipating H+-Gradients at Nano-Molar Levels

T riethyl lead (E t3P b +), a highly toxic oxidation p roduct of the anti-knock agent tetrae thy l lead (E t4Pb) was show n to act as anion (C L /O H ) an tip o rter in plant m em branes, dissipating energyd ependen t ion g rad ien ts , m em brane po ten tials, and consequently turgor. This m echanism was d em onstra ted w ith tonoplast-type vesicles isolated from coleoptiles of Zea mays L. The A TPdriven H + accum ulation within those vesicles was abolished already at nano-m olar levels of E t3P b +, but only in the p resence of C1“ . In intact cells the tu rgor dep en d en t indole-3-acetic acid induced elongation growth of coleoptile segm ents of A vena sativa L. was inhib ited by E t,P b + at m icro-m olar levels and afte r a lag of 15—20 m in. This lag m ight be due to a slow penetra tion of the agent through the waxy cuticle and the cell wall.