Ross J H, Lim L O, Krieger R I
Drug Chem Toxicol. 1979;2(3):193-205. doi: 10.3109/01480547908998242.
Duckweed (Spirodela oligorrhiza, Kurz) is a sensitive indicator of 1,1'-alkyl-4,4'-bipyridylium salt (viologen) herbicidal potency. A homologous series of viologens were tested to determine relative herbicidal potency which was related to alkyl inductive and steric effects of N-alkyl side chains. Chlorosis was assessed after 48 hr of continuous illumination to establish herbicidal potency. Herbicidally effective concentrations were 2.7, 12, 236, 71, 31, 51, 13 and 43 microM for methyl (paraquat), propyl, isopropyl, butyl, methyl-pentyl, hexyl, octyl and benzyl viologen, respectively. A biphasic relationship of herbicidal potency versus steric effect was established in which compounds with the least bulky side chains were most phytotoxic. Comparison of rat lethality (acute, subcutaneous) and herbicidal potency of these compounds indicates that none of the viologens tested are less toxic to mammals than plants compared to the commercial herbicide methyl biologen (paraquat).
浮萍（少根紫萍，库尔茨）是1,1'-烷基-4,4'-联吡啶鎓盐（紫精）除草效力的敏感指示物。测试了一系列同系紫精，以确定与N-烷基侧链的烷基诱导效应和空间效应相关的相对除草效力。在连续光照48小时后评估黄化情况，以确定除草效力。甲基紫精（百草枯）、丙基、异丙基、丁基、甲基戊基、己基、辛基和苄基紫精的除草有效浓度分别为2.7、12、236、71、31、51、13和43微摩尔。建立了除草效力与空间效应的双相关系，其中侧链体积最小的化合物对植物毒性最大。这些化合物的大鼠致死率（急性，皮下）与除草效力的比较表明，与商业除草剂甲基紫精（百草枯）相比，所测试的紫精对哺乳动物的毒性均不低于对植物的毒性。
