Peroxidase activities in the floral tissues of Tradescantia clone BNL 4430 treated with maleic hydrazide alone, X rays alone, or in combinations

Influence of climatic conditions on the mutations in pollen mother cells of Tradescantia clone 4430 and implications for the Trad-MCN bioassay protocol

The present was study aimed at investigating the influence of relative humidity and temperature on spontaneous and pollution-induced mutation rates during exposure and recovery periods in the Trad-MCN test. Cuttings of Tradescantia clone 4430 were exposed to a negative control, to 4 mM maleic hydrazide (MH), and to a polluted water sample under varying conditions of air temperature and humidity in climatic chamber experiments. The relative humidity did not affect the spontaneous mutation rate in the clone investigated, but was negatively correlated with the frequency of pollution-induced mutations. Low temperature caused an increase in the number of micronuclei in the negative control, but no comparable response in polluted samples. At an extremely high temperature, signs of strong physiological damage and/or of a meiotic delay of pollen maturation were detected. When the temperature increased gradually and the extreme value was maintained only for short time, such detrimental effects were not observed. Subsequent treatment with high and low temperatures, by contrast, resulted in the highest MCN rates of all experiments. Our studies point to the possibility of producing irregular results of the Trad-MCN test if the influence of climatic factors has not sufficiently been considered.

Further yearly analyses of spontaneous pink mutant events in the stamen hairs of tradescantia clone BNL 4430 cultivated in the NSC growth chamber

In order to confirm the results obtained in the previous 1-year-term (December 12, 1998, through December 10, 1999) scorings and analyses of spontaneous pink mutant events (PMEs) in the stamen hairs of Tradescantia clone BNL 4430 cultivated in a nutrient solution circulating (NSC) growth chamber, similar scorings and analyses were continued for another 52-week period from December 11, 1999, through December 8, 2000. The environmental conditions were not changed, except for a minor modification in the method of supplying the nutrient solution used. During the scoring period, 732,128 stamen hairs with an average cell number of 24.90 cells were observed, and 2,368 PMEs were detected. The overall spontaneous somatic mutation frequency was 1.35 +/- 0.03 PMEs per 10(4) hair-cell divisions, which was significantly lower than the value of 1.56 +/- 0.03 determined in the previous 52-week period, and the frequencies were lower during April through September than in other months, the period showing lower frequencies lasting 1-month longer than in the previous year. The present results reconfirmed the occurrence of a clear seasonal variation in the spontaneous mutation frequency in the NSC growth chamber, and the lower overall frequency, probably related to the minor modification in supplying the nutrient solution, is helpful for conducting mutagenicity tests at low levels, offering a lower background level. The analyses of the sectoring patterns of all these PMEs showed that the most of the 203 cases of multiple (two to five) pink sectors observed in the same stamen hairs (scored as 253 PMEs for calculating mutation frequency) were the results of events involving somatic recombinations occurred in single cells or cell lineages, rather than those of two or more independent somatic mutations occurred in different cells, agreeing with our previous study, and the significance of somatic recombinations in causing single PMEs was also reconfirmed.

Analyses of spontaneous pink mutant events in the stamen hairs of Tradescantia clone BNL 4430 cultivated in a nutrient solution circulating growth chamber

In order to obtain more fundamental data on Tradescantia clone BNL 4430, one of the most suitable testers for environmental mutagens, the occurrences of spontaneous somatic pink mutations in the stamen hairs were scored for 52 weeks from 12 December 1998 to 10 December 1999, cultivating the young inflorescence-bearing shoots with roots in a nutrient solution circulating (NSC) growth chamber. The environmental conditions in the chamber were 22.0+/-0.5 degrees C during the 16h day with the light intensity of 7.5klx from white fluorescent tubes, and 20.0+/-0.5 degrees C at night. During the scoring period, 697,443 stamen hairs with an average cell number of 25.36 were observed and 2642 pink mutant events (PMEs) were detected. The overall spontaneous mutation frequency was 1.56+/-0.03 PMEs per 10(4) hair-cell divisions, and the frequency was significantly lower in May, July and August and significantly higher in November and December. By analyzing the sectoring patterns of 1856 PMEs (70.25% of PMEs detected), the most of 172 cases of multiple (two to five) pink sectors observed in the same hairs (scored as 232 PMEs for calculating mutation frequency) were found to be the results of events involving somatic recombinations occurred in single cells or cell lineages, rather than those of two or more independent somatic mutations occurred in different cells. This finding clearly shows the significance of somatic recombinations in producing such multiple sectors (382 sectors in total) which occupied 19.0% of the 2006 pink sectors in total analyzed. Somatic recombinations were considered to be playing a significant role also in producing single PMEs in the stamen hairs.

Mutagenic interactions between X-rays and two promutagens, o-phenylenediamine and N-nitrosodimethylamine, in the stamen hairs of Tradescantia clone BNL 4430

Mutagenic interactions between X-rays and two promutagens, o-phenylenediamine (PDA) and N-nitrosodimethylamine (DMN), were studied in the stamen hairs of Tradescantia clone BNL 4430, a blue/pink heterozygote. The young inflorescence-bearing shoots with roots of this clone cultivated in a nutrient solution circulating growth chamber were used as tester plants. After determining dose-response curves for X-rays. PDA and DMN, combined treatments with PDA or DMN and X-rays were conducted, exposing acutely to X-rays 20 h before starting, at the midpoint of, or 20 h after completing the PDA or DMN treatments for 4 h. Clear synergistic effects in inducing somatic pink mutations were detected when X-rays were irradiated before the PDA or DMN treatments, resembling those confirmed earlier between maleic hydrazide (MH) and X-rays. On the contrary, clear antagonistic effects were observed when X-rays were given after the PDA or DMN treatments, also resembling those between MH and X-rays. When X-rayed at the midpoint of the PDA or DMN treatments, merely additive and synergistic effects were observed, respectively, differing from the antagonistic effects between MH and X-rays. The mutagenic synergisms detected were considered to be the results of interactions between DNA strand breaks (and the resultant chromosome breaks) induced by X-rays and those by PDA or DMN, whereas the mutagenic antagonisms observed were presumed to be due to X-ray-caused inhibition of the activation of PDA and DMN in the stamen-hair cells. The time periods required for penetrations into floral tissues and/or activations into mutagens seem different among PDA, DMN and MH.

Activation of aniline by extracts from plants and induction of chromosomal damages in Chinese hamster ovary cells

Activation of aniline by plant extracts was studied by a chromosomal damage induction assay in Chinese hamster ovary (CHO) cells in vitro. Extracts from roots of Vicia faba activated aniline and the activation caused increases in chromosomal aberrations (CAs) and endoreduplicated cells (ERCs), but did not cause sister-chromatid exchanges (SCEs). Extracts from Pisum sativum and Lactuca sativa, however, did not activate aniline. All C-hydroxylated metabolites of aniline, o-aminophenol, m-aminophenol and p-aminophenol, induced not only CAs but also SCEs in CHO cells. These results show that the pathway for aniline activation by Vicia extracts is by means other than the C-hydroxylation.