Factors Influencing the Penetration of Naphthaleneacetamide into Leaves of Pear (Pyrus Communis L.)1,2

Abstract Factors influencing the foliar penetration of naphthaleneacetamide (NAAm) were established by following penetration from a glass vial into pear leaf discs ( Pyrus communis L. cv. Bartlett). Penetration through the upper surface was linear for 96 hr, whereas, through the lower surface there was rapid penetration for 48 hr followed by a reduced rate. Uptake of NAAm was proportional to the concentration applied. Penetration was not influenced by pH of treatment solutions ranging from 3.0 to 7.0. Increasing temperature from 5–35°C caused a marked increase in penetration with Q 10 values ranging between 1.59 to 5.46. Increasing light intensity resulted in increased penetration through the lower surface up to about 300 ft-c, but had no effect on NAAm penetration through the upper surface. Penetration was greater through the upper than lower surface in expanding leaves, but the reverse was true when leaves were fully expanded. Tween 20 and Triton B-1956 (0.1%) increased NAAm penetration through the lower surface, but to a lesser degree than X-77 (0.1%). No surfactant studied enhanced penetration through the upper surface. Penetration from microdroplets was similar to that from solutions in glass cylinders until the droplets dried. Droplet drying resulted in an immediate increase in penetration.