CHARACTERIZATION OF A NORFLURAZON-RESISTANT MUTANT OF CHLAMYDOMONAS-REINHARDTII

A norflurazon-resistant mutant has been isolated from Chlamydomonas re inhardtii that showed a three-fold factor of resistance over wild type cultures. In comparison to wild type cultures, the mutant showed bett er retention of chlorophylls and carotenoids when grown in light in th e presence of norflurazon. When grown in the dark, chlorophyll losses were similar, while carotenoid losses were lower than in the wild type cultures. Higher levels of phytoene accumulated in the wild type cult ures in the presence of norflurazon than in the resistant cultures. Th e resistant cultures also showed cross tolerance to EMD-IT 5914, a her bicide with a similar mode of action. Norflurazon resistance in this a lga appears to arise from alterations in the target enzyme phytoene de saturase.