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The effect of soil amendment with the STOCKOSORB®500 MICRO hydrophilic polymer on the photosynthetic traits in beech seedlings (Fagus sylvatica L.) during 50 days of dehydration was investigated. Dehydration was detected through osmotic potential (Ψs) in the assimilatory organs of beech seedlings. The addition of Stockosorb positively affected the CO2 assimilation rate (A) and instantaneous water use efficiency (A/T), for severely drought-treated seedlings. In comparison with irrigated plants, the values of A of non-irrigated plants with Stockosorb substrate decreased by 50%, and in non-irrigated plants with common substrate by 88%. The fast kinetics of chlorophyll a fluorescence indicated chronic photoinhibition under drought treatment without Stockosorb, while no significant changes in maximal quantum efficiency (Fv/Fm) were recorded under drought treatment with Stockosorb. The actual quantum efficiency of PSII (ΦPSII) markedly decreased in both treatments - with and without Stockosorb, though significant differences were found only between control treatments and drought treatment without Stockosorb. Moreover, the thermal energy dissipation (NPQ) was strongly limited under severe drought stress. The capacity to down regulate PSII functionality through non-photochemical quenching was maintained under drought treatment with Stockosorb. The results indicate that an amendment with soil conditioner significantly improved the photosynthetic performance of drought-stressed beech seedlings.

Until recently, investigators had no idea how accurately cultivated microorganisms represented the overall microbial diversity. The cultivation-dependent approach is limited by the fact that the overwhelming majority of microorganisms present in soil cannot be cultivated under laboratory conditions. The development of molecular phylogenetics has recently enabled characterization of naturally occurring microbial biota without cultivation. There is a vast amount of information held within the genomes of cultivable and non-cultivable microorganisms, and new methods based on analysis of DNA allow to investigate this potential. In this work we show some aspects, advantages and disadvantages of classical and new approaches in taxonomical and functional description of bacteria present in natural microbial assemblages on the example of cultivable bacteria isolated from rhizosphere of plants, tobacco and black nightshade, planted in PCB contaminated soil. Biochemical analysis of isolates showed 8 different bacterial species. This identification was compared by discrimination using MALDI-TOF mass spectrometry and identity evaluation after sequencing of 16S rDNA. Six strains from original number of 8 were positively identified after 16S rDNA sequencing and their phylogenetic relations were compared. These analyses confirmed closed relations of all species (two of isolates exhibited the same characteristics and were discriminated as the same species Pseudomonas stutzeri) and also of Burkholderia xenovorans LB 400, a well-known PCB degrader. Nevertheless, only two isolates gave a positive reaction after amplification of the biphenyl dioxygenase gene and exhibited potential to degrade PCB. These results indicate that only a subset of the recovered molecular information, derived from active population based on molecular and functional analysis is relevant to microbial ecology.

Tobacco, Nicotiana tabacum L., var. Wisconsin 38 as the control (WSC), and four genetically modified lines of the same variety, were tested for Cd, Zn and Ni accumulation. Genetically modified lines of the same variety, bearing the transgene CUP1 (gene coding a yeast metallothionein), GUS (reporter gene for ß-glucuronidase), HisCUP (CUP combined with a polyhistidine tail), and HisGUS (reporter gene for ß-glucuronidase, combined with a polyhistidine tail) under a constitutive promoter, enabling it to follow the heavy metal tolerance and uptake changes as a function of the transgene present. Control and transgenic lines were tested for accumulation of risk elements on sand nutrient medium with the addition of cadmium, zinc and nickel. The results showed high Cd accumulation ability of HisCUP line. The Cd content in aboveground biomass was increased by 90% compared to the non-transformed control and Cd content in roots was decreased by 49%. Determination of Zn content in aboveground biomass did not confirm higher uptake by transgenic plants significant for phytoremediation. The Ni content was significantly increased in aboveground biomass of HisGUS construct. GUS construct introduced the ability to accumulate all investigated metals; the others accumulated only one in extended amount.