Effects of Fluridone and Norflurazon on Conditioning and Germination of Striga asiatica Seeds

Inhibitors of carotenoid biosynthesis are known to prevent abscisic acid (ABA) biosynthesis and to affect germination and dormancy of seeds in many plants. In this study, the effects of three carotenoid biosynthesis inhibitors, fluridone, norflurazon and diflufenican, on the conditioning and germination of Striga asiatica seeds were examined. Fluridone and norflurazon shortened the conditioning period required before S. asiatica seeds would germinate after exposure to the germination stimulant strigol, and prevented the inhibitory effects of both light and supraoptimal temperature (40 °C) on seed germination. In addition, treatment with fluridone or norflurazon after conditioning in water induced seed germination in a manner similar to the effect of natural germination stimulants. Moreover, the seedlings developing after conditioned with fluridone formed haustorium-like structures without the involvement of haustorium inducing factors. In contrast, diflufenican had no effect on the conditioning and germination of S. asiatica seeds. These results indicate that fluridone and norflurazon have various effects on the germination of S. asiatica seeds and might be available for control of root parasites.