Effect of chromate ions on marine microalgae Phaeodactylum tricornutum.

Effect of chromate ions on the culture of a marine diatom Phaeodactylum tricornutum was studied using an M-PEA-2 fluorimeter, which carries out simultaneous measurement of fluorescence induction and redox transformations of the P700 pigment within a millisecond range. Chromate ions were shown to inhibit electron transport in PS II and decrease the rate of QА reduction. This results in decreased values of the quantum yield of electron transport in PS II (ϕEo) and performance index (PI ABS), lower rates of P700 reduction, and increased energy (DI0/RC) and ΔpH-dependent nonphotochemical quenching (q E ). Emergence of the slow component of P700 reduction was observed, indicating the activation of cyclic transport in the presence of chromate. Performance index (PI ABS), which was the most sensitive parameter, may be recommended for detection of chromate ions at early stages of their toxic action. The fluorescence parameter F O is promising application in biotesting to assess the algal growth rates.

[Effect of Methylmercury on the Light Dependence Fluorescence Parameters in a Green Alga Chlamydomonas moewusii].

The effect of a dangerous toxic substance, methylmercury, on light dependence curves of chlorophyll fluorescence in Chlamydomonas moewusii was studied. We found low concentration of methylmercury (10(-7) M) to cause a decrease in the relative rate of the non-cyclic electron transport activity of PS 2, a decline in the maximum utilization of light energy (α), and a decline in the saturation light intensity (E(s)). Non-photochemical fluorescence quenching increased after short-term exposure and decreased in the course of prolonged incubation. These parameters were more sensitive to the action of the toxic substance than the widely used parameter F(V)/F(M), which reflects the maximum quantum yield of PS 2. We propose the use of the method of fast measurement of light dependence curves of fluorescence to detect the changes in algal cells at the early stages of exposure to mercury salts.

[Analysis of dominant-recessive mutated character of nfr genes of Chlamydomonas reinhardtii and its mutual interaction with the chloroplastic psbA gene].

Phenotypic analysis of the nfr/Nfr diplontic hybrids has demonstrated the recessive mutated character of the nfr genes, and the norflurazon resistant character of the Nfr-4 And Nfr-5 mutants were resulted in by the different nuclear genes nfr-1 and nfr-2 respectively. From the tetrad analysis result of hybridizations of psbA mutant with wild strains CC-124 and nfr mutant, it have been demonstrated that the sensitivity of psbA mutated strain to norflurazon under photoautotrophic condition is due to its multiple effect whereas the chloroplast genome under the mixotrophic situation also gives some effect for resistance to norflurazon. From the titration results of cross-resistant character for antibiotics of norflurazon resistant strains, we had found that, the Nfr-3 mutant has some cross-resistance to erythromycin and streptomycin; based on this phenomenon it would be expected that this mutant having resistant character to suppressor of phytoene desaturase also give some effect for construction of chloroplastic protein.