Concanavalin A Improves the Polyethylene Glycol Method for Fusing Plant Protoplasts

An improved method for polyethylene glycol-induced fusion of protoplasts isolated from auxotrophic mutants of Nicotiana tabacum L. cv. Gatersleben was developed. By using Petri dishes coated with concanavalin A the attachment of protoplasts induced by polyethylene glycol was strengthened. As a consequence of the stronger attachment more fusion products remained after the dilution and washing procedure. It was also found that a shorter treatment combined with a more rapid dilution of the polyethylene glycol solution was superior to previous fusion methods used for plant protoplasts.     

The Effect of Activated Charcoal on Tissue Cultures: Adsorption of Metabolites Inhibiting Morphogenesis

Cell suspensions of Daucus carota and Haplopappus gracilis and callus suspensions of Allum cepa var. proliferum were grown in media with and without activated charcoal. Differentiation occurred in those Daucus and Allium cultures that contained charcoal. It was shown by mass spectrometry that the media without charcoal contained high amounts of phenylacetic acid and p-OH-benzoic acid (Daucus), 2,6-OH-benzoic acid (Allium) and benzoic acid, pelargonic acid and caprylic acid (Haplopappus), whereas the media with activated charcoal did not. It was also shown that p-OH-benzoic acid had inhibitory effects on the embryogenesis in Daucus cultures.     

Effects of Activated Charcoal on Growth and Morphogenesis in Cell Cultures

The effects of activated charcoal on growth and morphogenesis in plate cultures of different plant cells have been studied. It was shown that medium containing charcoal induced embryogenesis in cultures of Daucus carota in which embryo formation could not be brought about by omitting auxin from the medium. Charcoal-medium also induced abundant root formation in older cultures of Allium cepa, which normally did not produce roots. The growth of cultures of Glycine max and Haplopappus gracilis was totally inhibited by charcoal. It is thought that activated charcoal removes substances from the medium, one of which might be auxin.     

Functional differences in epiphytic microbial communities in nutrient-rich freshwater ecosystems: an assay of denitrifying capacity

1. The denitrifying capacity of epiphyton was used to evaluate differences in the function of epiphytic microbial communities on submersed macrophytes in nutrient-rich freshwater ecosystems. The denitrifying capacity of epiphyton on Potamogeton perfoliatus shoots of different age and with different epiphytic abundances from a eutrophic lake was investigated in laboratory microcosms in the light and dark. Additionally, differences between epiphyton on shoots of Potamogeton pectinatus grown under different in situ nutrient and hydraulic conditions were investigated by examining their denitrifying capacity.
2. Denitrification was registered in well-developed epiphytic layers on both mature and senescent shoots in the dark, with activities 3- to 10-fold higher in the epiphytic communities of senescent shoots. No activity was detected on young shoots with sparse epiphyton or on shoots from which loosely attached epiphyton had been removed. Denitrification never occurred during illumination.
3. Even though the epiphytic abundance was similar in magnitude, the denitrifying capacity of epiphyton adapted to high nutrient loadings was about a hundred times higher than that of epiphyton adapted to lower nutrient levels. Additionally, epiphytic abundance and denitrifying capacity were higher at sites less exposed to wave turbulence or water currents, than at sites with more water turbulence.
4. The results illustrate how the hydraulic and nutrient conditions of the surrounding water affect both the quantity and function of epiphytic microbial communities in nutrient-rich freshwater ecosystems.