Effects of pyrazosulfuron-ethyl and imazaquin on the tuber formation and shoot tillering of yellow nutsedge (Cyperus esculentus L.).
Cyperus esculentus tubers were collected from upland fields of Utsunomiya University in Feb. 1994. Plants arising from tubers were treated with 0, 0.1, 0.3, 1, 3, 10 or 30 ppm pyrazosulfuron-ethyl and 0, 1, 3, 10, 30 or 100 ppm imazaquin at the 2.5-leaf-stage without tillers. All treatments contained 100 ppm of the nonionic surfactant Neoestrin. Plants were grown in the greenhouse at 20-30°C, and the number and fresh weight of newly formed tubers and the number of shoots were recorded 90 days after application. In the pyrazosulfuron-ethyl treatment, the number and the total and average fresh weight of tubers were decreased with increasing herbicide concentration, and no tubers were formed at 30 ppm; in contrast the number of shoots was increased at 1-30 ppm. Imazaquin showed similar effects; it decreased the total and fresh weight, and the number of tubers at 1-100 ppm, but increased the number of shoots at 100-300 ppm. In herbicide-treated plants, the growth of mature leaves which had already emerged at the time of application was hardly interrupted, while emergence or elongation of new leaves was significantly inhibited even at lower concentrations. It is suggested that the enhanced tillering in herbicide-treated plants may be closely related to changes in endogenous hormone, presumably auxin, balance.