Fig. 1 (a) Outer surface of the rhizosheath on an immature region of a field-grown crown nodal root. The root was excavated, shaken free to loose soil, and observed in a cryo-SEM; (b) a transverse face through a similar root and rhizosheath showing thickness of rhizosheath (R); and (c) a living hair root of the ericaceous species Lysinema ciliatum mounted in water. The 50-µm wide root is surrounded by expanded mucilage, which was produced by cells of tiny root cap. While in soil the mucilage contracted and held soil (arrows) tightly against the root surface. With permission, from the Annual Reviews of Plant Physiology and Molecular Biology, Volume 50, 1999, by Annual Reviews (http://www.AnnualReviews.org) (McCully, 1999)
Fig. 2 (a) Total phenolic content of 200 g of soil amended with 100 ml of 1:12, 1:8, and 1:4 (v/v, leaf leachate/water) leaf leachate of Pluchea lanceolata; and (b) natural soil infested with P. lanceolata from four sites (S1, S2, S3, and S4). Values for mean are significantly different from control at the levels of p < 0.05. Reproduced with permission from the editor of American Journal of Botany and National Research Council Canada. Source (Inderjit and Dakshini, 1994; Inderjit and Dakshini, 1996)
Fig. 3 Total phenolic content of 200 g of soil, from different textural class (clay loam, sand, silt loam, and sandy loam), amended with 100 mL of 1:12 (TS1), 1:8 (TS2), and 1:4 (TS3) (v/v, leaf leachate/water) leaf leachate of Pluchea lanceolata. Reproduced with permission from the editor of American Journal of Botany (Inderjit and Dakshini, 1994)
Fig. 4 (a) Total phenolic content of 200 g soil amended with four levels of leaf litter leachates of Kalmia angustifolia. A 5, 10, 15, and 25 g of K. angustifolia leaf litter was soaked in 400 mL of water to get different levels of leachate. Reproduced with permission from National Research Council Canada (Inderjit and Mallik, 1996); (b) total phenolic content of soil infested with K. angustifolia from uncut and cut black spruce forest and K. angustifolia–free soil from uncut black spruce forest. Similar letters indicate significant (p < 0.05) differences between values. Reproduced with permission from the editor of Acta Oecologia (Inderjit and Mallik, 1999)
Fig. 5 Spatio-temporal variation in soil juglone in a black walnut–corn alley cropping system. Juglone was quantified at 0, 0.9, 2.45, and 4.25 m (0 m represents the tree row and 4.25 m represents the middle of alley). Reproduced with permission from Kluwer Academic Press (Jose and Gillespie, 1998)
Fig. 6 Soil juglone concentration as a function of the distance from tree row (only `no barrier' treatment is used for this analysis). Error bars represent 1 SE of the mean. Reproduced with permission from Kluwer Academic Press (Jose and Gillespie, 1998)
