Both diazotrophs fixed N2 in a wide range of O2 levels. The nitrogenase activity of T2 is higher than 9°C and its optimum activity was at 10-15% O2. The respiration patterns were different in semisolid and liquid medium; this probably indicates different tolerance and protection mechanisms against O2.
The early stages (24 hours) of the interaction between roots and T2 cultures were characterized by an increased respiration rate of the roots and of the G. diazotrophicus cultures and by an increase in the activity of the enzymes SOD and GdP in the roots.
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