The allelopathy is a process for which products of the secondary metabolism, as terpenes phenolic, of a certain vegetal
intervene significantly, generally of antagonistic form, in the development of other species of plants. The objective of this
work was to chemically characterize the essential oil of
Lippia sidoides
Cham. growing in the Cariri cearense region,
Brazil, and evaluate the allelopathyc effect of this oil on the germination of lettuce (
Lactuca sativa
L.), arugula (
Eruca
sativa
Mill.), and cauliflower (
Brassica oleracea
L.), in pre-plantation application. The monoterpene thymol (84.90%) has
been identified as the principal constituent in the essential oil. The experiment was done in randomized complete block, in
4 × 3 factorial; being used four essential oil combinations applied in three different species in pre-plantation applications.
Emergence velocity index (EVI), germination percentage and mean time to germination (MTG), had been analyzed through
daily counting carried out until the 14
th day after sowing. Through qualitative analysis performed by gas chromatography
coupled with mass spectrometry (GC/MS) were identified seven chemical constituents representing 97.82% of essential oil
of
L. sidoides, being that the constituent present in greater concentration in oil was the thymol (84.90%). Could be verified
the occurrence of the negative allelopathyc effect of lettuce crop, because its present low EVI and greater MTG, for the
other vegetable species there were no allelopathic effect.
