Abstract
Promotive effects of four rice herbicides with different modes of action, pyrazosulfuron-ethyl, chlomethoxynil, pretilachlor and benzofenap, on the sprouting of lateral buds in Cyperus serotinus Rottb. tubers were examined.Although chlomethoxynil and benzofenap showed no effect, pyrazosulfuron-ethyl and pretilachlor increased the number of sprouting lateral buds. Pyrazosulfuron-ethyl was more effective than pretilachlor, and almost all of the lateral buds sprouted after treatment with this herbicide at 2g/10a. Furthermore, all of the other acetolactate synthase (ALS) inhibiting herbicides tested including bensulfuron-methyl, flazasulfuron and imazaquin also induced sprouting of lateral buds in C. serotinus tubers. The effect of bensulfuron-methyl was not eliminated by subsequently applied branched-chain amino acids, leucine, isoleucine or valine at 1 to 100ppm. These ALS inhibiting herbicides thus induce lateral bud sprouting and/or appear to eliminate apical dominance in C. serotinus tubers. Such an inductive effect on lateral bud sprouting may therefore be based on some interaction(s) between the herbicide and the plant hormones, presumably cytokinins, rather than on the depletion of branched-chain amino acids.
