VIEW ARTICLE

Physiology and Biochemistry

Occurrence of Juglone in Various Tissues of Pecan and Related Species. A. Borazjani, Former graduate assistant of Plant Pathology, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762 ; C. H. Graves, Jr.(2), and P. A. Hedin(3). (2)Professor of Plant Pathology, Department of Plant Pathology and Weed Science, Mississippi State University, Mississippi State 39762; (3)Research chemist, Boll Weevil Research Laboratory, USDA-ARS, Mississippi State University, Mississippi State 39762. Phytopathology 75:1419-1421. Accepted for publication 27 June 1985. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1985. DOI: 10.1094/Phyto-75-1419.

Measurements of the seasonal distribution of juglone (5-hydroxy-1,4-naphthoquinone) among various tissues of pecan (Carya illinoensis 'Van Deman') revealed that the highest concentrations occurred in the leaflets in June but in the nuts in September. The leaf rachis, twigs, twig bark, trunk, root, and root bark had lower concentrations at both dates. There were no changes in juglone content of twigs sampled at monthly intervals or differences among twigs of five pecan cultivars at any date. Very little juglone was detected within pollen of several hickories (including pecan). The concentration of juglone in husk, kernel, and leaflet of black walnut (Juglans nigra), shagbark hickory (Carya ovata), and four pecan cultivars were: in husks, walnut > hickory and pecan; in leaflets, walnut > pecan and hickory; and in kernels, walnut > hickory > pecan. Seedlings grown in greenhouse pots and girdled to the cambium had a higher concentration of juglone in the leaves than did nongirdled seedlings, suggesting that juglone was synthesized in the leaf area and translocated by the phloem.