Azolla-Anabaena's behaviour in urban wastewater and artificial media--influence of combined nitrogen.

The results of using the nitrogen fixing symbiotic system Azolla-Anabaena to improve the quality of treated urban wastewater, particularly on what concerns phosphorus removal efficiencies (40-65%), obtained in continuous assays performed during the past few years and presented earlier, were very promising. Nevertheless, the presence of combined nitrogen in some wastewaters can compromise the treatment efficiency. The main goal of this work was to compare plants behaviour in wastewater and in mineral media with and without added nitrogen. Azolla filiculoides's specific growth rates in wastewater and in mineral media without added nitrogen or with low nitrate concentration were very similar (0.122 d(-1)-0.126 d(-1)), but decreased in the presence of ammonium (0.100 d(-1)). The orthophosphate removal rate coefficients were similar in all the growth media (0.210 d(-1)-0.232 d(-1)), but ammonium removal rate coefficient in wastewater was higher (0.117 d(-1)) than in mineral medium using that source of nitrogen (0.077 d(-1)). The ammonium present in wastewater, despite its high concentration (34 mg NL(-1)), didn't seem to inhibit growth and nitrogen fixation, however, in mineral media, ammonium (40 mg NL(-1)) was found to induce, respectively, 18% and 46% of inhibition.

Localization of uricase in mycorrhizas of Ophrys lutea Cav.

Infected roots of Ophrys lutea present nymerous peroxisome profiles identified by diaminobenzidine (DAB) staining. The presence of uricase in these peroxisomes could also be recognized cytochemically. The activities of catalase and uricase, assayed using a crude fraction of peroxisomes, reached 0·8 µkat min-1 protein-1 and 1·73 nakat min-1 mg protein-1 respectively. The role of uricase in purine metabolism is discussed in terms of host/endophyte interactions in O. lutea mycorrhzas.

Impregnation of biological material by ZnI2-OSO4, KI-OSO4 and NaI-OSO4 mixtures for electron microscopic observations: chemical interpretation of the reaction.

Alkaline iodide-osmium tetroxide mixtures were used in an electron microscopic study of plant cells and gave better results in the preservation of the cell structure in contrast to the cell structure observed when ZnI2-OSO4 mixtures are used. The electron density observed in the reactive sites of the cell by OSO4-iodide mixtures is controlled by the presence and oxidation state of iodine that acts as a regulator of the potential redox of the reaction of OSO4 with the biological material.

Cytochemical localization of lipases during spore germination from Bryum capillare.

In the oil containing spores of Bryum capillare, lipid breakdown occurs within three days after sowing. The periods of activity of acid, neutral and alkaline lipases are coincident. They start at the first day after sowing the spores. After 3 days of germination, when storage fats forming large globules are mobilised no lipase activity could be detected any longer in the glyoxysomes. Acid lipase is preferentially located in spherosomal membrane but is also present at the glyoxysomal membrane. Alkaline lipase is specifically located in the glyoxysomes and mitochondria. A cooperation presumably exists between acid and alkaline lipases in the hydrolysis of monoglycerides at the glyoxysomal level. Neutral lipase activity is localized at the spherosomal membrane, in the endoplasmic reticulum and in dictyosomes. It is absent from glyoxysomes.