Rb
+
and K
+
in the xylem sap (J
Rb
and J
K
) were expressed as a
fl
ow
(
m
molg
1
FWrootd
1
or nmolg
1
FWrooth
1
) and were calcu-
lated using the ion concentration in the xylem sap, the xylem sap
volume, the fresh weight (FW) of the root, and the exudation time.
Rb
+
uptake by the root was calculated from the Rb
+
accumulated in
the rootplus Rb
+
inthexylemsapduringthe exudationperiod, and
the presented values refer to the fresh weight of the root and the
uptake time (
m
molg
1
rootFWd
1
)