incubated at 70 C
for 4 h,
and then cooled
at room temperature for1 h.
The contents
of the tubes
were
centrifuged at 10,050 g for 10 min.
An aliquot of 100 ml
of the supernatant
was diluted to 1 ml
with Milli-Q water.
The sodium concentration
was measured
using
graphite
furnace
atomic
absorption
spectroscopy (VarianSpectrAA 880 spectrophotometer; Varian, Palo Alto, California, USA).
The sodium concentration
in the plant tissue
was calculated using
a standard curve between 50 and 2000 mM of sodium.