普通小球藻对嗪草酮、骠马和甲草胺的敏感性研究

通过96h的毒性实验,研究了普通小球藻对3种不同作用机制农田常用除草剂嗪草酮、骠马和甲草胺的敏感性．结果表明。在实验条件下,嗪草酮、甲草胺对普通小球藻的毒性随时间的推移有加重趋势。并呈现很好的剂量效应关系;最高抑制生长浓度(嗪草酮0．24mg·L^-1,甲草胺12．8mg·L^-1)处理组的最大比增长率分别为对照组的12．38％和31．58％;骠马低浓度对普通小球藻的抑制作用不明显,并呈一定的生长促进效应,0．08mg·L^-1浓度组普通小球藻最大比增长率为对照组的111．44％,而高浓度则具有明显的生长抑制作用,并随时间推移,毒性逐渐减弱．嗪草酮、骠马和甲草胺的96hEC50分别为0．021、0．937和5．54mg·L^-1．普通小球藻对嗪草酮最敏感。其次为骠马和甲草胺．3种除草剂在实验条件下对普通小球藻叶绿素a含量的影响和对普通小球藻生长的影响相似。表现出较好的剂量．效应关系．     

Isolation and characterisation of metribuzin-resistant Chlamydomonas reinhardii cells

Chlamydomonas reinhardii cells were treated with 5-fluorodeoxyuridine and ethylmethanesulfonate to induce mutagenesis. The mutant cells were analyzed for resistance against metribuzin (4-amino-6-(t-butyl)-3-methylthio-1,2,4-triazine-5-one). Clones with normal growth were isolated and the mutant cells further characterized. The photosynthetic rates of the mutant cells were about 20% lower than those of wild-type cells. The mutant cells were not only resistant against metribuzin (pI₅₀ lowered from 6.65 to 3.41) but also against bromacil, atrazine, phenisopham and tolerant against 3-(3,4-dichlorophenyl)-1,1-dimethylurea. However, the mutant was more susceptible to phenolic electron-transport inhibitors like bromonitrothymol, ioxynil and i-dinoseb. 2,4-Dinitrophenyl-2′-iodo-3′-methyl-4′-nitro-6′-isopropyl phenyl ether inhibited the wild-type thylakoids more than the mutant. The analysis of the electron transport with artificial electron donors and acceptors showed that only Photosystem II was affected by the mutation and not Photosystem I. Binding experiments with isolated thylakoids of resistant and susceptible cells using [¹⁴C]metribuzin and [³H]-i-dinoseb revealed that metribuzin did not bind specifically to the thylakoids of the mutant cells, but that i-dinoseb did bind to the thylakoids of the mutant, and even better than to the thylakoids of the wild-type cells. Fluorescence studies confirmed these results.