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United States Department of Agriculture

Agricultural Research Service


item Elmore, Carroll
item Tonos, Jennifer
item Steele, Mark

Submitted to: International Symposium on Adjuvants for Agrochemicals
Publication Type: Proceedings
Publication Acceptance Date: 7/1/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: The wax on leaf surfaces affects the absorption, penetration, and ultimately, the efficacy of a pesticide spray solution. In this report we are using a technique developed in our laboratory to determine the exact chemical nature of this upper or outermost layer on a leaf surface. The procedure involves gently extracting only the outer or upper layer of wax, preparing samples and running an analysis using a simple benchtop gas chromatograph/mass spectrometer and a sophisticated computer software system to determine these leaf surface components. Additionally in this report we are looking at three soybean lines differing in pubescence. Generally the results indicate the leaf wax is composed of a mixture of many substances as are all leaf surface waxes from other plants. Soybean leaves lack secondary and tertiary alcohols, which are found in other plants, among other findings. Also, there are small but significant differences in the qualitative composition among the isolines. The significance of these results will be evaluated in further research.

Technical Abstract: Epicuticular wax is the outermost barrier to, and determinant of reaction to, pesticide spray deposition, spread, and penetration on leaf surfaces. Wax components on leaf surfaces vary among species and are thought to be instrumental in affecting the structural and functional aspects of the leaf. We are reporting on the composition of epicuticular wax from soybean nleaves with differing levels of pubescence (isolines of dense, normal and glabrous). The epicuticular wax consists of a mixture of simple aliphatic hydrocarbons (C20-C32), primary alcohols (C18-C34), carboxylic acids (C14-C34), saturated and unsaturated triterpenes, cinnamic acid derivatives, and the methyl ester of hexacosanoic acid. The presence of higher molecular weight fractions were not observed due to the 650 dalton limit of our mass analyzer.

Last Modified: 07/25/2017
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