Identification and effects of interaction phytotoxic compounds from exudate of cistus ladanifer leaves

Eleven allelochemicals (ferulic acid, cinnamic acid, 4-hydroxy-benzoic acid , hydroxycinnamic acid, methyl propionate, oxalic acid, methylmalonic acid, p-anisic acid, butyric acid, 1-hydroxybutyric acid, and azulene) were iden tified in the exudate of Cistus ladanifer L. We studied the effect of each on germination, cotyledon emergence, root length, and cotyledon length of R umex crispus. Three groups were distinguished with respect to phytotoxic ac tivity: compounds with low activity (ferulic acid, 4-hydroxybenzoic acid, o xalic acid, methylmalonic acid, p-anisic acid, hydroxybutyric acid, and azu lene), with intermediate activity (cinnamic acid and hydroxycinnamic acid), and with high activity (methyl propionate and butyric acid). The effect of the interaction of the compounds was studied. When acting conjointly, all combinations tested produced a more negative effect on both germination and seedling growth than when acting alone. The interaction affected cotyledon emergence and root length more negatively than germination and cotyledon l ength. When hydroxycinnamic acid and cinnamic acid were added to these mixt ures there was an enhancement in the phytotoxic activity, accentuating the effect of the other allelochemicals.