{'fraction_non_alphanumeric': 0.04314868804664723, 'fraction_numerical': 0.013994169096209912, 'mean_word_length': 4.447619047619048, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Multiple effects of salinity on photosynthesis of the protist Euglena gracilis

The effect of NaCI in the culture medium on growth, photosynthesis and cell content of chlorophyll, K + , Na + , Ca 2+ and Mg 2+ in Euglena gracilis was studied. O 2 production, quantum yield of photosystem II (PSII), the non-photochemical quenching of chlorophyll fluorescence (q N ) and the chlorophyll a/b ratio all diminished by 0.2 M NaCI. Respiration and chlorophyll a and b increased, whereas the photochemical quenching (q p ) of chlorophyll fluorescence was not affected by 0.2 M NaCI. Salt stress also induced an increase in cell volume and in K + and Na + concentrations, but decreased the concentrations of Ca 2+ and Mg 2+ . Except for a protective effect on O 2 production, additional Ca 2+ in the culture medium did not attenuate the salt effect on the parameters measured. The addition of HCO 3 - restored the PSII quantum yield of O 2 production in cells grown in high salt. Salt stress promoted a decrease in the apparent rate of quinone A (Q A ) reduction and an apparent obstruction of Q B reduction, which were not prevented by excess HCO 3 - ; the addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) did not increase chlorophyll fluorescence in salt-grown cells. These results indicate that photosynthesis in Euglena grown under salt stress exhibits: (1) diminution of the HCO 3 - -dependent water-splitting activity of PSII ; (2) inhibition of the electron transfer at the quinone pool level; (3) probable increase in thylakoid stacking (as indicated by the effect on the chlorophyll a/b ratio): and (4) dissipation of the H + gradient across the thylakoid membranes (as indicated by the decrease of q N ).