Sodium Stimulation of Uptake Hydrogenase Activity In Symbiotic Rhizobium

Abstract

Initial observations showed a 100% increase in Hruptake (Hup) activity of Rhizobium legumixosarum strain 3855 in pea root nodules (Pisum sativum L. cv Alaska) on plants growing in a baked clay substrate relative to those growing in vermiculite, and an investigation of nutrient factors responsible for the phenomenon was initiated. Signifiantly greater Hup activity was first measured in the clay-rown plants 24 days after germination, and higher activity was maintained relative to the vermiculite treatment until experiments were terminated at day 32. The increase in Hup activity was associated with a decrease in H2 evolution for plants with comparable rates of acetylene reduction. Analyses of the cLay showed that it contained more Na (29 versus 9 milligrams per kilogram) and less K' (6 versus 74 milligrams per kilogram) than the vermiculite. Analyses of plants, however, showed a lare increase in Na' concentration of clay-grown plants with a much smaller reduction in K concentration. In tests with the same organisms in a hydroponic system with controlled pH, 40 millimolar NaCI increased Hup activity more than 100% over plants grown in solutions lacking NaCI. Plants with increased Hup activity, however, did not have greater net carbon or total nitrogen assimilation. KCI treatments from 5 to 80 millimolar produced slight increased in Hup activity at 10 millimolar KC] and tests with other salts in the hydroponic system indicated that only Na strongly promoted Hup activity. Treating vermiculite with 50 millimolar NaCI increased Na concentration in pea plant tissue and greatly promoted Hup activity of root nodules in a manner analogous to the original observation with the clay rooting medium. A wider generality of the phenomenon was suggested by demonstrating that exogenous Na increased Hup activity of other R. kguminosarum strains and promoted Hup activity of R. meliloti strain B300 in alfalfa (Medicago sativa L.).The nitrogenase enzyme complex of procaryotes catalyzes a concurrent reduction of N2 and protons to produce NH3 and H2.Even under 5 M,4Pa of N2, the system continues to allocate at

Physiological and biochemical responses of the green algaPachycladella chodatii(SAG 2087) to sodicity stress

“…3. Kapulnik and Phillips [44] showed that the sodium ion stimulates hydrogenase activity in pea root nodules containing Rhizobium leguminosarum bacteria.…”

Development and Partial Characterization of Nearly Isogenic Pea Lines (Pisum sativum L.) that Alter Uptake Hydrogenase Activity in Symbiotic Rhizobium

“…In symbiotic rhizobia, the Hup system is affected by the host plant. Thus, environmental factors perceived by the plant, such as irradiance (6) and salinity (18), alter Hup activity. Unexplained effects of host plant genotype on Hup activity also occur in different plant species nodulated by the same rhizobia (10,12,19,21,23).…”