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The influence of pH 3-10 on the growth, motility and photosynthesis in Euglena gracilis was demonstrated during a 7-d cultivation. The cells did not survive at pH < 4 and > 8, highest growth rate being detected at pH 7. Motility followed a similar pattern as growth rate. Photosynthetic response curves were shown to be of the same type over the whole pH range. High respiration was characteristic for cells grown at pH 5 and 6, the lowest one at 7. At high and also at low pH more active respiration was found which can be considered as a protective response on proton stress. Respiration was not completely inhibited with potassium cyanide. Photosynthesis was the most effective at pH 6; lower and higher pH decreased photosynthetic efficiency. pH affected more the growth rate than the photosynthesis.

Effects of short-term (1 h exposure) and long-term (7 d exposure) aluminium stress on photosynthesis and reproductive capacity have been studied in Euglena gracilis strain Z. Following concentrations of Al tot (added as AlCl 3 ) were tested: 0.5 mg L -1 , 1.0 mg L -1 , 1.5 mg L -1 , 2.5 mg L -1 , 5.0 mg L -1 , 7.5 mg L -1 , 10.0 mg L -1 , and 15.0 mg L -1 Al, respectively. Growth rates at different aluminium concentrations did not show significant differences, except at 15.0 mg L -1 Al. Initial respiration was higher in long-term than in the short-term experiments. It is supposed that an energy-dependent mechanism of excretion of aluminium ions has been active in the stressed cells. Consequently, the cells of E. gracilis after longterm exposure to aluminium are believed to be more acclimatised to the aluminium stress. Photosynthetic efficiency (PE) has been negatively affected by aluminium in all experiments performed. Differences between control algae and those treated with aluminium were significant in all cases. PE in long-term experiments was in general significantly higher at all concentrations of aluminium studied, compared to the short-term experiments. The aluminium concentrations tested led only to a general decrease in PE while the level of decrease was not especially concentration-dependent. In general, aluminium tolerance of E. gracilis can be estimated as low, especially by short-term exposure. However, good acclimatisation capacity of this green flagellate to aluminium doses by long-term exposure can be supposed. Wirkungen von Kurz-und Langzeit-Aluminium-Stress auf Photosynthese, Respiration und Reproduktions-Kapazität eines einzelligen grünen Flagellaten, Euglena gracilisKulturen von Euglena gracilis werden über 1 h und über 7 d gegen 0.5 mg L -1 , 1.0 mg L -1 , 1.5 mg L -1 , 2.5 mg L -1 , 5 mg L -1 , 7.5 mg L -1 , 10 mg L -1 und 15 mg L -1 Aluminium aus AlCl 3 8exponiert. Die Wachstumsrate zeigt mit Ausnahme der höchsten Al-Konzentration keine Beeinflussung. Die initiale Respiration ist in der Langzeitexposition höher als im Kurzzeitexperiment. Als Ursache wird angenommen, dass unter Stresseinfluss ein energieabhängi-ger Mechanismus der Exkretion von Aluminiumionen in den Zellen induziert wird. Als Konsequenz sind die langzeitig exponierten Zellen von E. gracilis stärker an den Stress akklimatisiert. Die photosynthetische Effizienz wird durch Aluminiumionen unter allen Versuchsbedingungen gegenüber der Kontrolle signifikant negativ beeinflusst, wobei keine Konzentrationsabhängigkeit nachzuweisen ist. Im Langzeitexperiment war unter allen Versuchsbedingungen die photosynthetische Effizienz höher als im Kurzzeitversuch. Allgemein ist die Aluminium-Toleranz von E. gracilis als gering anzusehen, speziell im Kurzzeitexperiment, wäh-rend im Langzeitexperiment eine gute Akklimatisationskapazität angenommen werden kann.

The responses of the growth rate, motility, and cell shape in the green flagellate Euglena gracilis to different concentrations of waste water substances from the pulp and paper industry were tested in a long-term study (7 days). Samples before (uncleaned sample) and after (cleaned sample) the treatment in a cleaning system were studied. The influence of different doses of UV-B radiation on cell shape and motility was also investigated. No statistically significant effects of increasing concentrations of the waste substances both before and after the cleaning process (except inhibition by the undiluted uncleaned effluent) on the growth rate in E. gracilis were observed. Cell shape turned out to be an unreliable physiological parameter for assessing the toxicity at lower concentrations of waste water substances. No significant patterns could be observed in the response of the cell shape to the different concentrations of the waste water substances or to UV-B radiation. Motility has been concluded to be a more sensitive parameter than cell shape. However, no clear patterns were observed in the response of the motility to the different concentrations of the waste water substances studied. Increasing concentrations of the uncleaned sample demonstrated a defense against UV-B radiation, due to the high absorbance in the UV-B range, when effects on motility were examined. We conclude that contrary to the results reported in the literature earlier, cell shape and motility of E. gracilis are not universal physiological parameters for bioassessment at lower concentrations of toxic substances, including metals such as copper and zinc from the pulp and paper industry. The long-duration tests had, in general, higher significance than those of short duration.

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-Influence of different light regimes (plants grown in shade and in the sun) on respiration, activity of alternative respiratory pathway and carbohydrates content in mature leaves of Ajuga reptans L. was investigated. All experiments were carried out under natural conditions. Sun plants had higher respiration, activity of the alternative pathway and carbohydrates content compared to the shade plants. Additional experiments were performed in order to study effects of darkening as well as evolution of respiration and carbohydrates concentrations in leaves of A. reptans during the day. Darkening led to a decline in total respiration in all types of plants investigated. Activity of the alternative pathway remained unchanged by 20 % in the leaves of the shade plants. On the other hand, darkness led to a twofold decrease in the activity of the alternative pathway in the leaves of the sun plants. Content of soluble carbohydrates in the darkness did not change in the leaves of the shade plants while significantly decreased in the leaves of the sun plants. Total respiration in the mature leaves of the shade plants studied did not change significantly during the day. However, a significant increase in the total respiration was detected in the mature leaves of the sun plants in the evening and in the night. Activity of the alternative respiratory pathway did not change significantly in the leaves of the shade plants during the day and corresponds to ca 20 % of the total respiration. The sun plants examined exhibited significantly higher activity of the alternative pathway during the period of active photosynthesis. In general, activity of the alternative pathway varied in the sun plants between 30 and 35 % of the total respiration during the day. Content of soluble carbohydrates decreased significantly during the day in the mature leaves of the shade plants, while no statistically significant changes by the sun plants could be detected. It has been suggested that increase in respiration and activity of the alternative pathway in the sun plants tested can be controlled by the content of carbohydrates in leaves. No clear proposal could be done concerning mechanisms regulating alternative pathway activity in the shade plants of A. reptans.

Background: Heavy metals, especially copper, nickel, lead and zinc, have adverse effects on terrestrial and in aquatic environments. However, their impact can vary depending on the nature of organisms. Taking into account the ability of heavy metals to accumulate in sediments, extended knowledge of their effects on aquatic biota is needed. In this context the use of model organisms (often unicellular), which allows for rapid assessment of pollutants in freshwater, can be of advantage. Pentachlorophenol has been extensively used for decades as a bleaching agent by pulpand paper industry. Pentachlorophenol tends to accumulate in the nature. We aim to determine if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies of Chlamydomonas reinhardtii, a motile green unicellular alga. It is discussed if photosynthesis and motility can be used as sensitive physiological parameters in toxicological studies.