Table II. NR activity and NO production in M. truncatula-S. meliloti control and mutant nodules

M. truncatula control (GUS) and MtNR1/2 RNAi (MtNR1/2) plants were inoculated with S. meliloti 2011 or napA strains. NO production, expressed as relative fluorescence units, was measured under 1% oxygen. Data are means ± sd of four independent measurements. Asterisks indicate significant difference (*P = 0.05, **P = 0.01) when compared with the control (GUS/2011) according to Student’s t test.

VariableGUS/2011MtNR1/2/2011GUS/napAMtNR1/2 napA
NR activity (nmol NO2 min−1 g−1 fresh weight)6.56 ± 0.873.94 ± 0.87*4.69 ± 0.76*3.08 ± 0.57**
Percent of control100607147
NO production (fluorescence units h−1 mg−1 fresh weight)4.65 ± 0.842.54 ± 0.71*2.81 ± 0.39*1.33 ± 0.37**
Percent of control100546029