PARENT SESSION
Organized Oral Session 16: Allelopathy: Biochemical interactions among plants affecting community structure, exotic invasions and evolutionary theory
Organizer(s): A Mallik and R Callaway
Tuesday, August 9, 8:00 AM - 11:30 AM, Meeting Room 511 C, Level 5, Palais des congrès de Montréal
Dual role for an allelochemical: (±)-catechin from Centaurea maculosa root exudates regulates conspecific seedling establishment.
Perry, Laura*,1, Paschke, Mark1, Vivanco, Jorge1, 1 Center For Rhizosphere Biology, Fort Collins, Colorado, USA
ABSTRACT- Research on plant allelopathy has focused primarily on interspecific interference, but allelopathic compounds may also have other roles for the plants that produce them. We have found that (±)-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. Adding activated carbon, which adsorbs organic compounds, to soil around C. maculosa adults in the field increased C. maculosa seedling density by 85% 25 days after sowing, and by 43% 32 days after sowing, suggesting that organic compounds in C. maculosa soils inhibit or delay C. maculosa recruitment. Analysis of field soils near mature C. maculosa revealed that C. maculosa soils can contain exceptionally high (±)-catechin concentrations. Soil (±)-catechin concentrations averaged 1.55 mg g-1 dry soil, and 60% of samples contained ≥ 1.0 mg (±)-catechin g-1. In laboratory experiments, treatment with ≥ 1.0 mg (±)-catechin ml-1 reduced seedling root elongation by > 50%, indicating that field (±)-catechin concentrations are sufficient to inhibit C. maculosa recruitment. Treatment with ≥ 1.0 mg (±)-catechin ml-1 maintained in solution with 10% methanol also reduced C. maculosa germination by > 70%. Seed viability analyses indicated that (±)-catechin maintained in solution with methanol did not significantly reduce C. maculosa seed survival, suggesting that (±)-catechin inhibition of germination was due at least in part to delayed germination rather than seed mortality. Chemical regulation of C. maculosa recruitment suggests a dual role of (±)-catechin as an allelochemical and an autoinhibitor. Depending on the solubility of (±)-catechin in soil and on the duration of effects of (±)-catechin on C. maculosa 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.
Key words: allelopathy, autoinhibition, intraspecific interactions, spotted knapweed