The effect of the partial pressure of oxygen (PO2) on the formation of vesicles, which are thought to be the site of N2 fixation in Frankia, was studied in HFPCcI3, an effective isolate from Casuarina cunninghamiana. Unlike other actinorhizal root nodules, vesicles are not produced by the endophyte in Casuarina nodules. However, in culture under aerobic conditions, large, phase-bright vesicles ...

A method for acetylene inhibition measurements of denitrification in the field using micrometeorological techniques is presented. It is based on the monitoring of flux ratios from small (<5 m2) microplots. The method measures concentration profiles close to the surface, and from these the ratio of gradients, which can be assumed to be equal to the ratio of fluxes, is calculated. Acetylene has b...

Rates of nitrogen fixation (measured as acetylene reduction) in the rhizosphere of the seagrass Zostera noltjj were highly dependent upon plant photosynthetic activity being significantly stimulated at elevated CO2 concentrations and by light, both in the short-term and over diurnal cycles. Stimulation by light became insignificant when 5 mbl sucrose was added to the sediment porewater. indicat...