ELECTRIC SIGNALS RELEASED FROM ROOTS OF WILLOW (SALIX-VIMINALIS L) CHANGE TRANSPIRATION AND PHOTOSYNTHESIS

Using willow plants (Salix viminalis L.) raised from cuttings, electric excitability and signal transmission were investigated extra- and intracellularly. Following root stimulation, willow plants generate action potentials that are propagated throughout the plant at velocities of 2 to 5 cm sec-1. Shifts in CO2, 02 and H2O exchange indicate the arrival of a signal in the leaves. The hydroponically grown root system is stimulated by providing nutrients, hormones or pH-changes. While the application of nutrients, auxin and cytokinins commonly leads to an increase in both CO2-uptake rate and transpiration rate, abscisic acid and acidification from pH 7.0 to pH 4.0 cause a decrease in both CO2-uptake rate and transpiration rate. Following all applications the foliar gas exchange responded constantly after 3 min. It is calculated that this lag is too short for moving a signalling substance to the leaves via the transpiration stream. This indicates that rapidly evoked and propagated electric signals are the route whereby stimulations are transmitted.