| Abstract: | Abstract Growth regulators, pesticides, herbicides and macroelements applied to tree trunks are often translocated to the foliage. The feasibility of using bark dressings for supplying micronutrients to deficient trees was investigated using new laboratory screening methods and a field trial. Zinc was chosen as a model compound since soil and foliar applications of zinc to apple trees have not proven entirely satisfactory. Less than one per cent of zinc applied as zinc chloride to the scraped bark of excised apple twig sections could be forced out in the xylem exudate. Translocation of exogenous zinc only occurred during the first six days after application. Zinc was also translocated through the intact bark of apple twigs but the percentage of cases in which translocation was observed was reduced from 100% (in scraped bark) to circa 40%; furthermore, the amount of zinc translocated was reduced tenfold. Significant sinc translocation to the foliage was not observed in field trials consisting of trunk applications of zinc salts to intact and scraped bark of apple trees with first flush foliage. Factors influencing the passage of zinc and other chemicals from bark to foliage are discussed. |
