HJ Detoxification of Naphthalic Anhydride to Maize Treated with High Concentration of Monosulfuron

In order to search for the rational application of monosulfuron and avoid possible phytotoxicityto succeeding maize (Zea Mays L.), evaluate the effect of the main impurities in monosulfuron technical on the growth of maize, detoxification of naphthalic anhydride (NA) to maize treated with high concentration of monosulfuron were studied by laboratory pot bioassay, by determination of the activity of acetolactate synthase (ALS) and other physiological and biochemical indicators such as content of chlorophyll and proline. The results of bioassay indicated that maize CAU 3138 was tolerant to monosulfuron with IC50 84.38 μg/kg and Yedan 13 was sensitive to monosulfuron with IC50 6.42 μg/kg. Impurities in monosulfuron technical had little herbicidal activity on CAU 3138 and Yedan 13 with IC50 more than 619 μg/kg. ALS activity determination in vitro indicated that I50 of monosulfuron for inhibition of ALS activity in three maize cultivars was 15.15~66.73 nmol/L, while inhibition of monosulfuron to ALS in vivo was weak. Pot bioassay indicated that, 1 000 μg/mL of NA haddetoxification to maize cultivars Yedan 13 and CAU 3138 when treated with monosulfuron at high concentration of 171.44 μg/kg. Determination of free proline and chlorophyll indicated that NA did not affect the content of free proline and total chlorophyll of CAU 3138, a powerful resistant maize cultivar obviously. Under the stress of monosulfuron, NA obviously increased the free proline content of a less resistant maize cultivar Yedan 13, but the increase of total chlorophyll was moderate. This indicated that the detoxification of maize under the stress of monosulfuron has direct relation to the increasing of maize tolerance due to the application of NA.