5 research outputs found
Comparative algological and bacteriological examinations on biofilms developed on different substrata in a shallow soda lake
According to the European Water Framework Directives, benthic diatoms of lakes are a tool for ecological status assessment. In this study, we followed an integrative sample analysis approach, in order to find an appropriate substratum for the water qualification-oriented biomonitoring of a shallow soda lake, Lake Velencei. Six types of substrata (five artificial and one natural), i.e., andesite, granite, polycarbonate, old reed stems, Plexiglass discs and green reed, were sampled in May and in November. We analysed total alga and diatom composition, chlorophyll a content of the periphyton, surface tension and roughness of the substrata and carbon source utilisation of microbial communities. Water quality index was calculated based on diatom composition. Moreover, using a novel statistical tool, a self-organising map, we related algal composition to substratum types. Biofilms on plastic substrates deviated to a great extent from the stone and reed substrata, with regard to the parameters measured, whereas the biofilms developing on reed and stone substrata were quite similar. We conclude that for water quality monitoring purposes, sampling from green reed during springtime is not recommended, since this is the colonization time of periphyton on the newly growing reed, but it may be appropriate from the second half of the vegetation period. Stone and artificially placed old reed substrata may be appropriate for biomonitoring of shallow soda lakes in both spring and autumn since they showed in both seasons similar results regarding all measured features
Cd-Fe interactions: comparison of the effects of iron deficiency and cadmium on growth and photosynthetic performance in poplar
To check the importance of Cd-induced iron deficiency in Cd stress, symptoms of Cd stress were compared
with those of iron deficiency or the combination of these two stresses. Poplar plants grown in
hydroponics with Fe-EDTA (e) or Fe-citrate (c) up to four-leaf stage were treated for two weeks either by
the withdrawal of iron (Fedef), or supplying 10 µM Cd(NO3)2 in the presence (Cad) or absence of an iron
source (Fedef+Cad). Cadmium and iron content of leaves developing under the stress was in the order of
cCad>eCad>cFedef+Cad and cCad≈eFedef≈cFedef+Cad<eCad<cFedef, respectively. Growth inhibition
was much stronger in Cad than Fedef plants. The inhibitory effects on CO2 fixation, maximal and
actual efficiency of PSII, chlorophyll synthesis, as well as the stimulation of the accumulation of violaxanthin
cycle components and increase in non-photochemical quenching were the strongest in cFedef+Cad
plants, otherwise these parameters changed parallel to the iron deficiency of leaves. Tendency of changes
in thylakoid composition were similar under Cad treatments and strong iron deficiency: particularly PSI
and LHCII decreased. Therefore, the development of the photosynthetic apparatus under Cd stress was
mainly influenced by the Cd-induced strong iron deficiency, while leaf growth was affected primarily by
the presence of Cd