Spontaneous action potentials in Lupinus angustifolius L.

with supplement

Abstract

Extracellular electrical potential measurements were applied to perform electrophysiological analyses of narrow-leaved lupin (Lupinus angustifolius L.). Spontaneous action potentials (SAPs) were investigated during three-day long Ag/AgCl electrode registration in the lupin stem under light/dark (LD), continuous light/light (CLL), and continuous very low light (CVLL). The average number of SAPs recorded during one day was approx. 5-7 per plant in the LD and CVLL conditions and on average approx. 9-20 SAPs per plant during the entire three-day measurements. No SAPs were recorded in the CLL conditions. The amplitude, half time of duration, velocity of propagation, time between two subsequent SAPs, and direction of propagation were described. Spontaneous APs propagated faster in CVLL (approx. 6 cm min^-1) than SAPs in the LD conditions (approx. 4 cm min^-1). In the CVLL conditions, spontaneous bursts of APs occurred more frequently (144 min. interval) than in the LD variant (233 min. interval). SAPs propagating from the roots and from the bottom of the stem towards the plant apex were the most common action potentials (85%). The spontaneous APs in lupin were visualized and drawn using a new informatics tool SAP Tracker. The hypothetical mechanism of SAP generation in intact lupin plants is discussed.