The Effect of Some External Factors on Nitrogenase Activity in the Free‐Living and Endophytic Nostoc of the Liverwort Blasia pusilla

Abstract

The effects of pH, light intensity, temperature, oxygen and dehydration on nitrogenase activity in the free-living and endophytic Nostoc sp. of Blasia are described. The endophyte exhibits greater nitrogenase activity at lower pH's than the free-living alga. Maximal activity in the free-living alga is attained at much lower light intensities than those required by the endophyte. Both algae have low activities below IO°C, the free-living alga showing high activity above 12°C and the endophyte above 17°C. Increasing pOj levels cause a decrease in activity in both algae. The free-living alga is more tolerant to dehydration than the endophyte, although both algae are protected by mucilage. The results are discussed and possible benefits resulting from the symbiosis, with respect to nitrogen fixation rates, considered.

Light‐induced hydrogen evolution by blue‐green algae (Cyanobacteria)

“…However, when Nostoc 'nuscorum is cultivated at lower temperature (~ 22°C), "ydrogen and ethylene evolution of the cells are strik-'ngly higher than with cell material grown at 32°C. This l^as also reported for the endophytic Nostoc from the liverwort Blasia pusilla (Rodgers 1978). Furthermore, a constant assay temperature, the molar ratio of "ydrogen evolved/acetylene reduced is higher with cells°f a culture grown at 22°C than with cells of a 32°C culture (Ernst et al 1979).…”

Bryophyte interactions with other plants

“…to accidental associations with epiphytic bacteria. The former symbioses form one of the few examples of bryophyte interactions that have been studied intensively with reference to morphology, anatomy, cytology, physiology and ecology (Peters el al., Rodgers, 1978).…”

Lichen refugia within sub-boreal spruce forests: The role of riparian alder swales.

“…Our results, however, are not without precedents as low temperature optima for nitrogenase activity have been observed in experiments not susceptible to these criticisms (Rodgers 1978;Lennihan et al 1994). These low optimal temperatures for fixation have been suggested to occur in cool climates (Rodgers 1978;Lennihan et al 1994).…”

“…These low optimal temperatures for fixation have been suggested to occur in cool climates (Rodgers 1978;Lennihan et al 1994). Seasonal acclimation may also be an important factor leading to the different temperature optima of ARA in these species, as has previously been found in rates of nitrogen fixation in Peltigera rufescens (Hitch and Stewart 1973) and in free-living Nostoc (Lennihan et al 1994).…”