Medium pH, EC, and nitrogen uptake
Medium pH measured after autoclaving was 5.71
and 6.18, respectively with and without AC (data not
shown), and it changed during shoots cultivation. The
presence of AC in the medium had a significant buffer-
ing effect on pH (ranging from 5.53 after 20 days to 5.08
after 40 days of culture) while the pH values dropped
to a value lower than 4.60 in the medium lacking AC
(Table 2).
After autoclaving, the EC value was 5.20 dS m-1 in
the medium with AC and 4.77 dS m-1 in the medium
without AC (data not shown) and these values were
affected by the presence of AC (Table 2).
The uptake of nitrate was higher for the shoots
grown on the medium containing AC with respect to
the control without AC while the ammonium uptake
was not affected by the treatments (Table 2).
Both AC treatment and the length of the culture
had a significant effect on ammonium to nitrate uptake
ratio. In fact, this ratio was significantly lower for the
treatment with AC (0.88 and 0.70 after 20 and 40 days
of culture, respectively) respect to the control without
AC (1.34 and 1.10 after 20 and 40 days of culture,
respectively).