Characteristics of FC-induced changes of transmembrane potential in maize roots FC(fusicoccin) a glucoside very active in promoting cell enlargement and proton secretion also induces an increase of the negative transmembrane potential in pea internode segments, squash cotyledons, maize coleoptiles and maize roots segments. In maize roots segments maximum hyperpolarization values ore obtained with concentrations of FC higher than 5.10-5M, with 5.10-5M FC the period of time required for reaching maximum value is of ca.6 min. The hyperpolarizing effect of FC is not influenced by the osmolarity of the medium and by the rate of cell enlargement. Low temperature(6 C} induces a rapid decrease in PD both in the controls and in the FC-treated samples, FC-induced PD is more temperature sensitive than basal PD, thus suggesting that effect of FC is metabolism dependent. FCCP and DNP induce a rapid and marked decrease of PD, larger in the FC-treated samples than in the controls. This can be interpreted as a consequence eiter of the incoupling of oxidative phosphorylation and thus of the decrease of ATP for ATPase involved in electrogenesis, or of a direct effect of FCCP and DNP on permeability of plasmalemma to proton. Partial anaerobiosis such markedly inhibit PD in the controls, does not prevent the hyperpolarization effect of FC. The effect of FC on PD is dependent on the ionic composition of the medium: K+ and ,at lesser extent, Rb+ at concentration higher than 5.10-4 M induce a rapid depolarization(new level is reached ca. 5 min. after change of the external cation concentration}, larger in presence than in absence of FC. In absence of K or Rb PO showed a constant tendency to increase, and in the medium containing Na, K + free, the maximal PD FC-induced is observed. In this condition Na+ is ineffective when present at concentration up to 10 mM; 30mM Na+ induces a clear depolarization in the PD probably due to the high driving force of the negative PD; 100 mM Na+ induces a rapid depolarization larger in the presence of FC than in the control. Li+ and Cs+ did not influence PD when present at con- centration up to 10 mM; at 30 mM depolarizing activity becomes apparent for Cs and at 100 mM for Cs and Li , also for these cations the depolarizing activity was much larger in the presence of FC. FC markedly increased the monovalent cation uptake rates at low salt concentration this effect is much larger for K+ and Rb+ than for Na+ and Cs+ ;the rate of cation uptake is only qualitatively related to depolarizing activity. The selectivity of the transport system for K+ and Rb+ as compared to the other cation is markedly increased by FC. These results are in agreement with the hypothesis that FC-induced hyperpolarization of PD is a consequence of the activation of a proton/ cation exchange mechanism having a high affinity for K+ .
Characteristics of FC-induced changes of transmembrane potential in maize roots / M. Cocucci, A. Ballarin Denti, S. Scacchi - In: The 9 International Conference on Plant Growth substances[s.l] : International Conference on Planth growth substances, 1976. - pp. 57-57 (( Intervento presentato al 9. convegno International Conference on Plant Growth Substances tenutosi a Lausanne nel 1976.
|Titolo:||Characteristics of FC-induced changes of transmembrane potential in maize roots|
COCUCCI, MAURIZIO (Primo)
|Settore Scientifico Disciplinare:||Settore AGR/13 - Chimica Agraria|
|Data di pubblicazione:||1976|
|Tipologia:||Book Part (author)|
|Appare nelle tipologie:||03 - Contributo in volume|