NITROGEN-FIXING HOMOGENATES OF MYRICA-PENSYLVANICA (BAYBERRY) NON-LEGUME ROOT-NODULES

A procedure was developed for preparing active N2-fixing (C2H2-reducing) homogenates of root nodules from the non-legume Myrica pensylvanica L. Plants were grown in sand culture and inoculated with a crushed nodule suspension. Homogenates were prepared by freezing and crushing 4-6 month old nodules to a fine powder in liquid N2. The homogenate was taken up in buffered sodium dithionite under Ar. Such homogenates reduced up to 2 μmol C2H2 h-1 g-1 fresh nodule for at least 3 h when assayed anaerobically in the presence of ATP, Mg2+, and sodium dithionite. All activity was particle bound. Acetylene reduction was prolonged by sequestering inhibitory phenolics with solid polyvinylpolypyrrolidone. Highest responses were obtained with 30 mm ATP and Mg2+ and 150 mm sodium dithionite. The high concentrations of ATP, Mg2+, and sodium dithionite required may indicate barriers to the uptake. The temperature optimum was between 25-28°C. Activity was retained after storage for 30 min at -10, 5° and 10°C but was lost at 50°C and reduced by 60% at 27°C. The preparation of active C2H2-reducing homogenates from this symbiotic association opens the way to further physiological and biochemical studies on the bayberry nitrogenase. © 1979.