The authors thank Verónica Feuring for her technical assistance
with HPLC and J. Döbereiner (EMBRAPA, Brazilian Enterprise
for Research on Agriculture) for providing us with the Azospirillum
brasilense strain FT326. This research was supported by
grant UBACyT (G052 and 20020100100278) to J.A.C. and UBACyT
(20020090200144) to C.M.R. and scholarship from the University
of Buenos Aires to M.N.