DETERMINATION OF FOLIAR UPTAKE OF CHEMICALS - INFLUENCE OF LEAF SURFACE MICROFLORA

Analysing uptake and desorption kinetics of methylglucose in needles of Picea abies (L.) Karst., the effect of NaN3 on methylglucose uptake, and the correlation between different degrees of colonization of needle surfaces with epiphytes and equilibrium uptake of methylglucose, showed that methylglucose was taken up only by epiphytes but not by the needles themselves. Thus, amounts of methylglucose taken up are a measure of the amounts of epiphytic microorganisms. Uptake of methylglucose into epiphytes was very rapid and equilibrium was obtained within 2h. Amounts taken up could completely be desorbed again from epiphytes within 2-6h. It is pointed out that the possible influence of leaf surface microorganisms must be considered in studies of foliar uptake of chemicals, in order to avoid erroneous conclusions.