Oxygen limitation of N2 fixation in stem‐girdled and nitrate‐treated soybean

• DOI: 10.1111/j.1399-3054.1988.tb09201.x
• Publication Date: 2007-07-13T12:06:00Z
• Authors: J. Kevin Vessey; Kerry B. Walsh; David B. Layzell
• Keywords: Girdling

The effects of increasing rhizosphere pO 2 on nitrogenase activity and nodule resistance to O diffusion were investigated in soybean plants [ Glycine max (L.) Merr. cv. Harosoy 63] which (EC 1.7.99.2) activities inhibited by (a) removal the phloem tissue at base stem (stem girdling), (b) exposure roots 10 m M NO 3 over 5 days (NO ‐treated), or (c) partial inactivation an nodulated 100 kPa (O ‐inhibitcd). In control had been treated with , concentrations increments from 20 70 did not alter steady‐state activity. contrast, depressed girdling resulted a recovery 57 67%, respectively, initial, rates This suggests that stem‐girdled ‐treated soybeans was ‐limited. For each treatment, theoretical values for into nodules estimated measured CO exchange, assuming respiratory quotient 1.1 0 infected cells. At external pressure ‐ displayed 4 8.6 times higher than those plants. ‐inhibited plants, increases 2.5‐ 3.9‐fold increase little effect either respiration but 2.3‐ 3.2‐fold These results are consistent stem‐girdling ‐inhibition treatments limiting supply causing apparent insensitivity .