Spray application factors and plant growth regulator performance: III. Interaction of daminozide uptake, translocation and phytotoxicity in bean seedlings

Effects of droplet size and carrier volume on foliar uptake and transport o f daminozide were investigated. A constant dose of daminozide (100 mu g per leaf) was applied to both primary leaves of 10-day-old Phaseolus vulgaris (cv Nerina) in droplet sizes of 1-10 mu l and carrier volumes of 10 to 200 mu l per leaf. Decreasing droplet size or increasing carrier volume decreas ed daminozide penetration, but increased translocation. Plotting the logari thm of the leaf surface/droplet interface area vs daminozide uptake yielded a negative linear relationship, but for translocation an optimum quadratic type relationship was obtained. Some phytotoxicity occurred at low carrier volumes and large droplet sizes. The degree of phytotoxicity was positivel y related to the amount of daminozide deposited per unit wetted area above 0.7 mu g daminozide mm(-2). Below this threshold, there was no visual evide nce of phytotoxicity. At the breakpoint, the deposit covered an area of 276 mm(2) on both primary bean leaf surfaces. Since the maximum in the relatio nship of translocation with interface area was in close agreement with the threshold amount of deposit above which phytotoxicity occurred, the inverse relationship between daminozide uptake and translocation at low interface areas was attributed to phytotoxicity. (C) 2000 Society of Chemical Industr y.