Abstract
In our previous experiment, it was strongly suggested that the main contributing factor for induction of Magoyakesyo (a physiological disorder occurring in greenhouse cucumbers cultivated by the pinching technique in Miyazaki Prefecture) is a result of high zinc absorption. Its symptom is known as a suppression of new shoots. However, it was assumed to be a complex action with copper and/or spreading agent rather than zinc only. Therefore, the interactions among zinc, copper and spreading agent on Magoyakesho were investigated. Cucumber seedlings 23 days old after grafting were hydroponically cultured under various concentrations and combinations of zinc, copper and spreading agent. Zinc was added as zinc sulfate at 3 concentrations: 0.1, 2.5 and 20mg L^<-1>. Copper was sprayed on leaves as Bordeaux mixture or copper sulfate solution at 2 concentrations: 0 and 500mg L^<-1>. The usual and latest spreading agents were used when agrochemicals were being sprayed. The results showed that zinc concentrations in leaves and tips of new shoots distinctly increased proportionally with increasing zinc concentration in the hydroponic solution. Elongation of the main and lateral new shoots was considerably suppressed in high zinc concentration treatments and was more pronounced in treatments where the latest spreading agent was used. The influence of both copper agents such as Bordeaux mixture and copper sulfate solution on the elongation of lateral shoots could not be clearly distinguished.
