Evidence for allelopathic interference of Japanese honeysuckle (Lonicera japonica) to loblolly and shortleaf pine regeneration

Abstract

Japanese honeysuckle presents a serious problem to the economically attractive natural regeneration of loblolly and shortleaf pine. This research investigated the potential allelopathic interference mechanisms of Japanese honeysuckle in relation to pine regeneration and growth, which may provide insight into overcoming this problem. The allelopathic potential of root exudates and leaf litter from Japanese honeysuckle was tested against loblolly and shortleaf pine seedlings. When Japanese honeysuckle and loblolly pine seedlings were grown using the same irrigation reservoir, there was no significant effect on the growth of either pine species. Exudates of Japanese honeysuckle grown as a pure culture in donor cups also produced no growth effects on pure-cultured pine seedlings grown in acceptor cups. In other assays, aqueous extracts of Japanese honeysuckle leaf tissue were toxic to duckweeds at concentrations well below levels where plasmolysis might cause effects. When Japanese honeysuckle leaf tissue was added to soil at a rate of 2 g tissue 100 g−1 soil, mean seedling height at 128 d after planting was reduced by as much as 40%. Moreover, pine seedlings grown in the presence of Japanese honeysuckle tissue exhibited significant chlorosis of the shoot and needles. Gas chromatography–mass spectroscopy analyses and high-performance liquid chromatography of Japanese honeysuckle leaf tissue aqueous extracts confirmed the presence of five compounds previously identified as possible allelochemicals: 4-hydroxycinnamic acid; 2-hydroxycinnamic acid; 3,4-dihydroxybenzoic acid; 3,4-dihydroxycinnamic acid; and chlorogenic acid. Results indicate that allelopathy plays at least a partial role in Japanese honeysuckle interference with loblolly and shortleaf pine.

A potential novel source of information for screening and monitoring the impact of exotic plants on ecosystems

“…These compounds are similarly the source of allelopathic interactions among plants (Inderjit and Keating 1999), and indeed, allelopathic interactions have been implicated in the spread and invasiveness of several exotics (Callaway and Bais et al 2003;Kogar and Bryson 2004;Prati and Bossdorf 2004;Skulman et al 2004, Vivanco et al 2004). Indeed, Inderjit and Keating (1999) list 112 weedy species, including many of those on the database used for this study and those cited above, as plants shown to have allelopathic activities.…”

Leaf and root extracts of the invasive shrub, Lonicera maackii, inhibit seed germination of three herbs with no autotoxic effects

“…Allelopathy has been suggested as a mechanism for exotic plant invasion in many species (Lawrence et al 1991;Roberts and Anderson 2001;Bais et al 2003;Hierro and Callaway 2003;Skulman et al 2004). L. maackii is an important invader in the eastern and midwestern U.S., but the potential for direct chemical effects of L. maackii on neighboring plants has been little studied.…”

“…In one study, incorporation of Lonicera japonica (Japanese honeysuckle) leaves into soil reduced the growth of loblolly and shortleaf pine, an effect that may be related to several phenolic secondary metabolites found in the tissues (Skulman et al 2004). In the other study, Trisel (1997) showed that aqueous extracts of L. maackii leaves could reduce the germination of green ash and sugar maple.…”

“…Thus, both leaves and roots may be sources of allelochemicals and extractions in water are most ecologically relevant. Although some good examples of root-mediated allelopathy in invasive plants exist (e.g., Bais et al 2003), roots are often neglected in studies of allelopathy by invasive plants (Lawrence et al 1991;Roberts and Anderson 2001;Trisel 1997;Skulman et al 2004). Second, we examined effects of these extracts at four ecologically relevant concentrations, relative to a control, which is important in determining causal relationships and minimizes effects due simply to unnaturally high doses of putative allelochemicals.…”

The biology of Canadian weeds. 135. Lonicera japonica Thunb.

“…The second major colonization event hypothesized by was that extensive growth of L. japonica in response to greater light effectively allows it to form a new ground layer, which may suppress the reproduction of overstory dominants and kill small trees and shrubs. The rapid development of populations of L. japonica may also result from its allelopathic effects on trees (Skulman et al 2004) and herbs Friedland and Smith 1982;Davison and Forman 1982). Suppression of dominant species may lead to positive feedback that converts the forest to an open vine-dominated disclimax (Little 1961;Whigham 1984).…”