Phytotoxic effects of volatile and water soluble chemicals of Artemisia herba-alba

We investigated the phytotoxic effects of volatile and water soluble chemicals produced by the shrub Artemisia herba-alba Asso. We conducted a number of germination and early seedling growth bioassays on species that co-exist with A. herba-alba in natural semiarid plant communities (Salsola vermiculata L. Lygeum spartum L. Pinus halepensis Mill. and A. herba-alba itself). In addition, we assessed the phytotoxic effects of a mixture of phenols that were identified in the aqueous extract of A. herba-alba on the germination of such species. We found that volatile chemicals inhibited the germination of P. halepensis seeds, promoted the growth of P. halepensis seedlings and reduced the root biomass of S. vermiculata seedlings, while water soluble chemicals promoted the growth of L. spartum and P. halepensis seedlings. On the other hand, both volatile and water soluble compounds inhibited the germination of A. herba-alba seeds, highlighting its strong autotoxic nature. We did not find a phytotoxic effect of phenols identified (catechol, protocatechuic and vanillic acids) on species that co-exists with A. herba-alba, although they had a moderate autotoxic effect. Our results suggest that both the volatile and water soluble chemicals might be involved in chemical interactions among plants in semiarid environments.