Abstract
The ability of roots of intact olive plants to change the pH of the external medium was studied. When the roots were put in contact with 1 mM CaSO4, a basification was recorded. The same behaviour was observed in the presence of 10 mM K+. The presence of NO3- and NH4+ caused basification and acidification of the external medium, respectively; this effect was reversed by subsequent addition of 0.5 mM vanadate. The results of the present work suggest that in olive plants changes in the pH of the solution surrounding the roots are dependent on uptake and metabolism of nitrogen ions.