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Histochemistry and Isolation of Gossypol and Related Terpenoids in Roots of Cotton Seedlings. M. E. Mace, Research Plant Pathologist, U.S. Department of Agriculture, Agricultural Research Service, Southern Region, National Cotton Pathology Research Laboratory, P.O. Drawer JF, College Station, Texas 77840; A. A. Bell(2), and R. D. Stipanovic(3). (2)(3) Research Plant Pathologist, and Research Chemist, respectively, U.S. Department of Agriculture, Agricultural Research Service, Southern Region, National Cotton Pathology Research Laboratory, P.O. Drawer JF, College Station, Texas 77840. Phytopathology 64:1297-1302. Accepted for publication 30 April 1974. DOI: 10.1094/Phyto-64-1297.

Gossypol (8,8-dicarboxaldehyde, 1,1,6,6,7,7-hexahy-droxy, 5,5-diisoprophyl,3,3-dimethyl,2,2-binaphthalene) and four related terpenoid aldehydes, 6-methoxygossypol, 6,6-dimethoxygossypol, hemigossypol (1,6,7-trihydroxy, 5-isopropyl, 3-methyl,8-naphthaldehyde), and 6-methoxyhemigossypol were identified in roots of 1-wk-old Acala 4-42 cotton seedlings. Histochemical procedures revealed the localization of these terpenoids in the epidermis and in scattered cortical parenchyma cells of the healthy tap root. The compounds were not detected in the first 3 cm back of the root tip. Gossypol and related terpenoid aldehydes appear to occur in cytoplasmic granules in the root epidermis and cortex. No lysigenous, terpenoid-containing glands were detected in seedling root tissues. The possible interactions of the five terpenoids with pathogens of cotton are discussed.

Additional keywords: Verticillium, Gossypium, cytochemistry, polyphenol, phytoalexin, antibiotic.