Retracted: Dual role for an allelochemical: (±)‐catechin from Centaurea maculosa root exudates regulates conspecific seedling establishment

Abstract

Summary1 Plant allelopathic compounds may have other roles than interspecific interference. We investigated whether (±)-catechin, a phytotoxin exuded from the roots of the exotic invader Centaurea maculosa (spotted knapweed), is also one of the factors that regulates C. maculosa recruitment. 2 Adding activated carbon, which adsorbs organic compounds, to soil around C. maculosa adults in the field increased seedling density by 78% 25 days after sowing, and by 34% 32 days after sowing, suggesting that soil-borne compounds inhibited or delayed recruitment. 3 Analysis of field soils near mature C. maculosa revealed that they can contain exceptionally high (±)-catechin concentrations (mean = 1.55 mg g −1 dry soil, with 60% of samples containing ≥ 1.0 mg (±)-catechin g −1 ). 4 In laboratory experiments, treatment with ≥ 1.0 mg (±)-catechin mL −1 reduced seedling root elongation by > 50%, indicating that field concentrations are sufficient to inhibit C. maculosa recruitment. Provided that 10% methanol was used to maintain (±)-catechin in solution for > 1 day, treatment with ≥ 1.0 mg mL −1 also reduced C. maculosa germination by > 70%. 5 (±)-Catechin maintained in solution with methanol did not significantly reduce C. maculosa seed survival, suggesting that inhibition of germination was due, at least in part, to delayed germination rather than to seed mortality. 6 Depending on the solubility of (±)-catechin in soil and on the duration of its effects on recruitment, C. maculosa may avoid intraspecific competition or regulate the timing of seedling establishment by reducing seedling growth or postponing germination in response to its own phytotoxin. 7 Chemical regulation of C. maculosa recruitment, as demonstrated here, suggests a dual role of (±)-catechin as an allelochemical and an autoinhibitor. The potential for a single plant root exudate to influence both inter-and intraspecific interactions emphasizes the complex effects that plant secondary metabolites may have on plant population and community structure.

Phytotoxicity, not nitrogen immobilization, explains plant litter inhibitory effects: evidence from solid‐state 13C NMR spectroscopy

“…Such an explanation probably does not apply in our case, because applications of mineral solution did not have promoting effects. Alternatively, we suggest that AC may neutralize an autotoxic factor(s) released in the root exudates (Webb et al, 1967;Singh et al, 1999;Perry et al, 2005), or may act as a cue for germination and seedling growth, as reported for charred wood and smoke (Keeley & Fotheringham, 1998). Further, although indirect, support for the phytotoxic hypothesis derives from the response of seedling shoot : root ratios to litter addition.…”

Functional Characterization of Proanthocyanidin Pathway Enzymes from Tea and Their Application for Metabolic Engineering

“…Likewise, the ANR protein from grape also produced (+)-E (Gargouri et al, 2009, and the two CsANRs exhibit higher amino acid sequence identity to VvANR (79% and 83%) than to MtANR or AtANR (64%-73%). In contrast to the widely distributed and well-documented (+)-catechin and (2)-E isomers, there are only a few reports of the presence of (2)-catechin and (+)-E in plants, such as (2)-catechin from Chamaebatia foliolosa and Centaurea maculosa (Nahrstedt et al, 1987;Bais et al, 2003;Perry et al, 2005) and (+)-E from Palmae spp. and Paullinia cupana (Delle Monache et al, 1972;Yamaguti-Sasaki et al, 2007).…”

Nature and role of root exudates: Efficacy in bioremediation

“…Autotoxicity has been widely observed in agricultural crops and weeds, as well as in some plants that inhabit natural systems. Phytotoxic root exudates appear to mediate autoinhibition in at least some of these species, including Asparagus officinalis (garden asparagus), Cucumis sativa (garden cucumber) (Yu et al, 2003) and Centaurea maculosa (spotted knapweed) (Perry et al, 2005).…”