The Absorption, Translocation and Breakdown of Schradan Applied to Leaves, Using 32p‐labelled Material

When 32P‐labelled schradan was sprayed on the leaves of apple stocks and seedlings, broad and runner beans, Coleus and chrysanthemums, some was absorbed, some evaporated and the rest remained for a considerable time on the leaf surface as a residue removable by aqueous leaching. Absorbed material is defined as that present on or in the plant and not removable by aqueous leaching at the time of harvest. Evaporation losses even from glass slides were lower than theoretical expectation, from leaves they were much less. It is possible that some breakdown of the schradan occurs within the cuticular layer. Comparisons of the absorption rates of upper and lower surfaces of leaves support the theory that absorption proceeds through the cuticle in preference to vapour phase entry through the stomata. Temperature and illumination have important effects on absorption. Young leaves have been shown to be generally more absorptive than the older leaves. Comparisons have also been made of the absorption by different species. Such data must be accepted with caution as, although physical conditions were the same for all the species within an experiment, the physiological stage of development of the different plant species will not be strictly comparable.