LAUSR

ABSTRACT Sago palm (Metroxylon sagu Rottb.) photosynthetic performance was evaluated under drought conditions through leaf gas exchange and chlorophyll a fluorescence measurement. Drought has an impact on sago palm’s leaf gas exchange parameters and its chlorophyll fluorescence of PSII. Stomatal limitations were found to be the main factor limiting photosynthetic activities of sago palm under drought conditions. Photosynthetic rate decreased following the inhibition in the PSII reaction center. Early detection of interference upon the efficiency of the PSII reaction center due to drought stress was recorded by chlorophyll a fluorescence measurement. Graphical abstract Abbreviations: CF/I–light response curve of chlorophyll a fluorescence, C i–intercellular CO2 concentration, E–transpiration rate, Eopt–optimum irradiance, ETR–electron transport rate, ETRmax–maximum electron transport rate, gs –stomatal conductance, I max–maximum irradiance, NPQ–non-photochemical quenching, P N–net photosynthetic rate, P N/I–light response curve of net photosynthetic rate, P N (Imax)–maximum value of P N obtained at maximum irradiance, WUE–water use efficiency, Y (II)–effective quantum yield of PSII, α–asymptotic photosynthetic efficiency, Φ(Icomp-I200)–quantum yield at the range between light compensation point and 200 µmol m−2 s−1 irradiance.