Abstract: Lactuca serriola, a national class quarantine object, is a new invasive species in the coastal area of Southeast China. The coenological survey showed that because of its big individual, L. serriola could easily form dominant population in its invaded area, and its main accompany species were Conyza canadensis, C. bonarinisis, Bidentis bipinnata, Oenothera laciniata, Ipomoea hederacea, Setaria viridis, Daucus carota, Xanthium sibiricum, Erigeron annuus, L. indica, Humulus scandens, Solanum nigrum and Aster sublatus. The measurements with LC-A4 portable photosynthesis and transpiration system (ADC, England) revealed that the net photosynthetic rate of L. serriola was as high as 21.22±0.45 μmol CO₂·m^-2·s^-1, being slightly lower than that of E. annuus and C. bonarinisis, similar to that of C. canadensis, and higher than that of Chenopodium album, Plantago virginica and L. indica. Based on the photosynthesis-light response equation, the theoretic light compensation point of L. serriola was 37.58 μmol m^-2·s^-1, its theoretic light saturation point was 1 480 μmol·m^-2·s^-1, and theoretic maximal net photosynthetic rate was 20.81 μmol CO_2·m^-2·s^-1. A distinct “noon break” phenomenon was observed in L. serriola photosynthesis, which might result from the high stomatal resistance against high light intensity and temperature. The main factors affecting the net phot-osynthetic rate of L. serriola were leaf photosynthetic active radiation, stomatal conductance, and leaf transpiration rate.

Key words: Liriomyza sativae, Secondary substance, Petroleum spray oil, Parasitoids, Population control