Context-dependent induction of allelopathy in plants under competition

Some plants use allelopathy to compete against neighbouring plants, and the ability to induce allelopathic compound production in response to competition is hypothesized to be adaptive, as plants can save costs of metabolite production in the absence of competitors. However, whether plants induce allelopathy has rarely been explored so far. We studied the inducibility of polyacetylenes—putative allelopathic compounds in Solidago altissima—in response to competition. Polyacetylenes were found in natural soil surrounding S. altissima patches within the range of concentration known to inhibit competitor growth. Individual S. altissima plants with higher polyacetylene concentration in roots suppressed the growth of the competitor plants more, suggesting that root polyacetylene levels proximate plants’ allelopathic capacity. Competition induced polyacetylenes in a context-dependent manner: Whereas introduced Japanese and Australian populations of S. altissima had higher constitutive concentr...