Physiological Responses of Paddy Weeds to Bensulfuron-methyl Herbicide

Abstract

This study was conducted to compare the susceptibility among weed species to bensulfuron-methyl, ALS (acetolactate synthase) activities and to determine the several physiological characteristics in the treated plants. Chlorophyll contents in Oryza sativa, Ludwigia prostrata, and Bidens tripartita were increased as the concentration of bensulfuron-methyl increased to 10 μM in media. A notable increase in the reducing sugar content was observed in Aneilema keisak and L. prostrata. Effect of bensufuron-methyl treatment on soluble protein content was different in tested plants. The free amino acid contents in L. prostrata and B. tripartita which are susceptible to this herbicide was significantly increased as the bensulfuron-methyl concentration was increased, however, there was no clear relationship between the free amino acid content and the degree of resistance to sulfonylurea herbicide. The acetolactate synthase activity measured in vitro was decreased drastically as bensulfuron- methyl concentration increased. The I50 values by bensulfuron -methyl for ALS from four tested plant species ranged from 28 nM to 39 nM. Our results of response spectrum and physiological response to sulfonylurea herbicide in Korean weeds may give some clues to set up the appropriate practical schedule for weed control in direct seeding field.