Permeation of organic molecules of widely differing solubilities and of water through isolated cuticles of orange leaves

Abstract

Water penetrated through isolated leaf cuticles of dwarf orange (Citrus mitis Blanco, 'Calamondin') as undissociated molecules because both [ I 8 0 3 water ('H2'80) and HTO (lH3H160) permeated at the same rate. HTO penetrated to 3 to 21% of the theoretical equilibrium value (TEV) in an unstirred system within 10 days for astomatous cuticles and 50 to 60% of TEV for stomatous cuticles. The permeability coefficient (k) of HTO through astomatous cuticles at 25°C was 6.8 x cm s-l.Two highly water-soluble 1%-labelled compounds, trichloroacetic acid (TCA) and 1,2,4-triazol-3-ylamine [aminotriazole (BSI) or amitrole (ISO)], and two nearly water-insoluble 1%-labelled compounds, 1-naphthyl methylcarbamate (carbaryl) and 2,6-dichloro-4-nitroaniline (dicloran), were compared to HTO as a reference standard in permeation studies. All four organic molecules permeated without decomposing. The relative k values for TCA, aminotriazole, carbaryl, HTO and dicloran were 0.32, 0.47, 0.71, 1.0, and 1.5 respectively. Although this suggested that the permeation of organic molecules may be inversely related to water solubility, this could not be established with certainty due to large variations in the data. The k values were obtained for 12 other organic compounds through a variety of biological and model membranes or were calculated from the literature. Any relationships between k and various molecular characteristics were unclear because a wide variety of cuticle sources and experimental design was used by different investigators working in this area. The calculation of k is considered essential in all permeability studies so that comparisons can be made between laboratories.

Basis for Antagonism in Mixtures of Bromoxynil Plus Quizalofop-P Applied to Yellow Foxtail (Setaria glauca)

“…The treated leaf was washed in 20 ml deionized water for 1 min to remove herbicide remaining on the leaf surface. The treated leaf was then blotted dry with tissue paper and washed for 1 min in chloroform to remove herbicide in the epicuticular wax (Davis et al 1979). Each plant part was homogenized separately in 20 ml methanol using a plain glass grinder or a mortar and pestle and filtered under vacuum.…”

Behavior of BAS-9052 OH in Soybean (Glycine max) and Johnsongrass (Sorghum halepense) Plant and Cell Cultures

“…Technical 4-14 C-BAS-9052 OH was obtained with specific activity of 13.9 mCi/mmol 5 . Immediately prior to application, a stock solution of 1 4 C-BAS-9052 OH containing 3.25 /iCi/ml was prepared in a volume of 1 ml of water containing 1% crop oil 6 , or in 1 ml of hexane.…”

“…Fresh weights of each plant part were obtained. The 1 4 C present on the surface of the treated leaf was removed by dipping the leaf for 1 min in distilled water, and the 1 4 C present in the epicuticular wax layer was removed by a similar 0.5-min chloroform wash (5,16). Plant parts were then homogenized separately in methanol and filtered.…”

Penetration of clopyralid and related weak acid herbicides into and through isolated cuticular membranes of Euonymus fortunei

“…Typically, two model systems have been used to understand the penetration of herbicides or other xenobiotics into and through cuticular membranes. The first system involves measuring the rate of transfer of herbicides from a donor solution through a cuticular membrane into a receiver solution (Kamimura & Goodman, 1964;Kannan, 1969;Baker & Bukovac, 1971;Bukovac et al, 1971;Robertson, Parham & Bukovac, 1971;Davis et al, 1979) while the second system measures sorption from a donor solution into a cuticular membrane (Shafer & Bukovac, 1987;Shafer et al, 1988), These model systems are somewhat unrealistic because they do not take into account the atmospheric phase that affects drying of the spray droplet and the surface deposit characteristics of different herbicide formulations (Hess, Bayer & Falk, 1981). An alternative approach which more closely approximates the conditions on the leaf surface is to apply a small drop of herbicide solution to a cuticular membrane which is placed in contact with an underlying aqueous medium such as agar (Solel & Edgington, 1973).…”