The pH of root juice was measured using a pH-meter (Orion-
Research Inc., model 701 Al Digital Ioanalyzer, Cambridge, MA,
USA). Soluble solids were measured at 20 ◦C using a digital refractometer
(model Brix PR-1, Atago CO., LTD., Tokyo, Japan) and
expressed as ◦ Brix, following the sampling procedure described in
the manufacturer’s manual (Schneider, 1979).