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Disease Control and Pest Management

Penetration of Selectively Toxic Aromatic Hydrocarbons Into Crown Gall Tumor Cells. Larry W. Moore, Assistant Professor, Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331; Milton N. Schroth, Professor, Department of Plant Pathology, University of California, Berkeley, CA 94700. Phytopathology 66:1460-1465. Accepted for publication 8 June 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1460.

Crown gall tumor cells on tomato plants were killed selectively by a mixture of five aromatic hydrocarbons in paraffin oil (STO) without killing the adjacent stem cells. The selective toxicity is attributed to enhanced penetration of tissues and tumor cell walls rather than differential permeability of cellular membranes of diseased and healthy tissues. Tritiated 2,3-dimethylnaphthalene penetrated deeper into tumors than healthy stems and could be detected intracellularly only in tumor cells. Differential tissue penetration also was indicated by more rapid and greater nonspecific electrolyte leakage from excised treated tumors. When tissues were infused with STO containing Sudan IV dye, the intercellular spaces of treated stems remained filled with the colored STO for 3 weeks without damage, but tumors were rapidly penetrated and killed. Apparently, the STO was unable to penetrate the stem cells. A major difference between tumor and stem tissues was the absence of a differentiated epidermal layer over the tumors. This allowed rapid loss of water from tumors by evaporation, thus reducing aqueous barriers to incoming STO. Callose, a possible barrier to STO, was not detected in the cell walls of stems. Lipid materials that might aid penetration were not found in the cell walls of tumors. Once past the cell wall, some tumor cell tonoplasts were ruptured within 1.5 hours after treatment with STO. Membrane damage in treated tumor cells was detected much earlier (within 6 minutes) by measuring nonspecific electrolyte leakage from treated tissues.