Green algal cell suspensions are used in agrochemical research for screening herbicides. This paper reports on the inhibitory effects of 39 herbicides from 19 different chemical classes with nine different modes of action on green algae cultured in liquid media. The results show that herbicide screening using Chlorella as a model organism is simple, quick, and sensitive. In vitro systems can be a second screening net to ensure that potential new structures are not missed. A set of biotests using cell suspension cultures of Chlorella are suggested as a herbicide prescreen to eliminate inactive compounds before testing on higher plants in the greenhouse. The method has been shown to be suitable for the requirements of microscreen and high-throughput screening (HTS) in vitro. A large-scale microscreen has been devised, which cultures algal cells using self-made Erlenmeyer flasks containing 5 ml of liquid medium. They are particularly useful for HTS compounds with dissimilar modes of action.

In the present study the biodiversity of the most abundant phototrophic organisms forming biological soil crust communities were determined, which included green algae, diatoms, yellow-green algae and lichens in samples collected on Ardley and King George islands, Maritime Antarctic. The species were identified by their morphology using light microscopy, and for lichen identification thin layer chromatography as also used to separate specific secondary metabolites. Several sources of information were summarized in an algae catalogue. The results revealed a high species-richness in Antarctic soil crust communities with 127 species in total. Of which, 106 taxa belonged to algae (41 Chlorophyta, nine Streptophyta, 56 Heterokontophyta) and 21 to lichens in 13 genera. Moreover, soil crust communities with different species compositions were determined for the various sampling locations, which might reflect microclimatic and pedological gradients.

54 strains of viable green algae and 26 strains of viable cyanobacteria were recovered from 128 and 56 samples collected from Siberian and Antarctic permafrost, respectively, with ages from modern to a few million years old. Although species of unicellular green algae belonged to Chlorococcales were subdominant inside permafrost, green algae Pedinomonas sp. were observed in Antarctic permafrost. Filamentous cyanobacteria of Oscillatoriales, Nostocales were just found in Siberian permafrost. Algal biomass in the permanently frozen sediments, expressed as concentration of chlorophyll a, was 0.06–0.46 μg g−1. The number of viable algal cells varied between <102 and 9×103 cfu g−1, but the number of viable bacterial cells was usually higher from 102 to 9.2×105 cfu g−1. Frozen but viable permafrost algae have preserved their morphological characteristics and photosynthetic apparatus in the dark permafrost. In the laboratory, they restored their photosynthetic activity, growth and development in favourable conditions at positive temperatures and with the availability of water and light. The discovery of ancient viable algae within permafrost reflects their ability to tolerate long-term freezing. In this study, the tolerance of algae and cyanobacteria to freezing, thawing and freezing–drying stresses was evaluated by short-term (days to months) low-temperature experiments. Results indicate that viable permafrost microorganisms demonstrate resistance to such stresses. Apart from their ecological importance, the bacterial and algal species found in permafrost have become the focus for novel biotechnology, as well as being considered proxies for possible life forms on cryogenic extraterrestrial bodies.

Fourier-transform infrared (FTIR) spectroscopy was carried out on single colonies of Pediastrum duplex present in air-dried preparations of mixed phytoplankton samples isolated from a eutrophic freshwater lake. FTIR absorption spectra had 12 distinct bands over the wavenumber range 3300–900 cm−1 which were tentatively assigned to a range of chemical groups, including -OH (residual water, wavenumber 3299 cm−1), -CH2 (lipid, 2924), -C=O (cellulose, 1739), amide (protein, 1650 and 1542), >P=O (nucleic acid, 1077) and -C-O (starch, 1151 and 1077). Measurement of band areas identified residual water, protein and starch as the major detectable constituents. Areas of single bands and combined bands of -CH2, -C-O and >P=O species normalized to protein (to correct for differences in specimen hydration and thickness) showed wide variation between colonies, indicating environmental heterogeneity. Correlation analysis demonstrated close statistical associations between different molecular species. Particularly high levels of correlation between bands 3/4 (CH2), 6/7 (amide) and 8/9 (-CH3) was consistent with their joint origin from the same molecular species. The isolation of bands 11 and 12 in the correlation pattern was confirmed by factor analysis, suggesting that variation in the level of starch is statistically unrelated to other macromolecules being monitored. The use of FTIR spectroscopy to characterize an algal micro-population within mixed phytoplankton has potential for future studies on biodiversity and environmental interactions at the species level.

Successive extraction of the green alga, Scenedesmus acutus 276–3a with different solvents indicated that the petroleum ether extract was the most repellent to the hatched larvae of Spodoptera littoralis. The application of spray emulsified 1 % petroleum ether extract inhibited egg laying. At 0.25% concentration the moths laid only 52.4 of their egg masses on the treated oviposition sites in comparison to the untreated control. Concentration of 1% was protective against the immature stage by hindering the third instar larvae to feed on treated leaf discs. In addition, the water emulsion of petroleum ether extract was insecticidal. The percentage mortality was directly proportional to the concentration applied and to the duration of exposure.