Volatile constituents of essential oils isolated at different growth stages from threeConyza species growing in Greece

The essential oils isolated at vegetative, flowering and flowering–fruiting stages of three Conyza species growing in Greece were analysed by GC–MS; 54 constituents were identified. The oils of C. albida were rich in limonene (10.0–21.1%), germacrene D (10.5–20.2%) and cis-lachnophyllum ester (8.8–36.5%). The oils of C. bonariensis were rich in limonene (8.3–15.1%), (E)-β-ocimene (11.5–18.9%), cis-lachnophyllum ester (10.8–21.2%) and matricaria ester (9.4–17.5%). The oils of C. canadensis were rich in limonene (50.0–70.3%) and (E)-β-ocimene (4.0–7.5%). The oils showed significant variations among the growth stages. These variations can be used for distinguishing the three species.