Black walnut juglone

Juglone [481-39-0] (Cl Natural Brown 7 Cl 75500) was isolated from the husks of walnuts in 1856 (50). Juglone belongs to the Juglandaceae family of which there are a number of species Jug/ans cinerea (butter nuts), J. regia (Persian walnuts), and J. nigra (black walnuts). Persian walnuts were known to the ancient Romans who brought them over from Asia Minor to Europe. As early as 1664, the American colonists knew how to extract the brown dye from the nuts of the black walnut and butternut trees, both native to eastern North America (51). 

The toxic influence exerted by Juglans nigra (black walnut) on other plants has been attributed to 5-hydroxy-1,4-naphthoquinone (juglone) (11,31). Hydrojuglone is present in the root bark, leaves, and fruit husks. This compound is not considered toxic, but it is oxidized to the toxic juglone upon exposure to air (51). Rainfall... 

To gain more understanding of the European alder decline and because of our concern about the future growth of black walnut planted with nitrogen-fixing species, a study was initiated to measure soil juglone concentration and to estimate the number of Nitrobacter and Nltrosomonas bacteria in a black walnut plantation containing plots of black walnut alone and in mixture with European alder and autumn-olive. 

The mean juglone concentration in soil beneath plots of autumn-olive/ black walnut was significantly lower than in soil beneath European alder/black walnut and black walnut-alone plots (Table I). Juglone concentrations also differed with sampled depth (Table I). Significantly higher concentrations were present at the 0-8 cm depth than at lower depths. 

Table I. Juglone Concentration in Soil According to Depth and Treatment in a Mixed Planting of Black Walnut and Nitrogen-fixing Species...

Juglone (5-hydroxy-1,4-naphthoquinone) is a water-soluble yellow pigment that is exuded from leaves, fruits, bark, and roots of black walnut Juglans nigra), English walnut (J. regia), and hickory (Carya ovata) trees, among others. 

Juglone, a dye known for centuries, is produced from the husks of hlack walnuts. It is also a natural herbicide (weed killer) that kills off competitive plants around the black walnut tree but does not affect grass and other noncompetitive plants. The formula for juglone is C QHg03. 

Juglone, a natural herbicide, is produced from the husks of black walnuts. 

The black walnut tree has often been observed to inhibit the growth of numerous species of plants (see Table 18.11). The area of inhibition usually corresponds closely with the spread of the root system. Juglone (5-hydroxynaphthoquinone), which is present in both the roots and aerial parts of the plant is thought to be the toxic factor. 

Jose, S. and Gillespie, A.R. (1998) Allelopathy in black walnut (Juglans nigra L.) alley cropping. I. Spatio-temporal variation in soil juglone in a black walnut-corn (Zea mays L.) alley cropping system in the midwestem USA. Plant Soil 103, 191-197... 

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