Table III. NO3 and NO2 reductase activities in nodules and bacteroids of M. truncatula plants

M. truncatula wild-type plants were inoculated with S. meliloti 2011, napA, or nirK strains. The inhibition of NR activity by Tg in nodule and bacteroid preparations was checked after a 4-h incubation period in the presence of the inhibitor. nd, Not detected. Asterisks indicate significant difference (*P = 0.05) when compared with the control (2011) according to Student’s t test.

NR or NiRNoduleBacteroid
2011napAnirK2011napAnirK
nmol NO2 min−1 g−1 fresh wtnmol NO2 min−1 mg−1 protein
NR
 Control9.7 ± 1.26.1 ± 1.2*8.5 ± 0.80.13 ± 0.02nd0.11 ± 0.03
 +1 mm NaTg1.4 ± 0.30.01 ± 0.01
NiR18.5 ± 2.316.0 ± 4.311.5 ± 2.7*1.12 ± 0.071.25 ± 0.08nd