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.Abbreviations: CF/I-light response curve of chlorophyll a fluorescence, C i -intercellular CO concentration, E-transpiration rate, E opt -optimum irradiance, ETR-electron transport rate, ETR maxmaximum electron transport rate, g s -stomatal conductance, I max -maximum irradiance, NPQnon-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, WUEwater 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.

<p>Iron toxicity affects the growth and yield of rice plant. Overcoming the damage of rice production by iron toxicity requires furthermore researches from laboratory to field levels. Here, we study responses of rice genotypes to iron toxicity between vegetative stage in hydroponic and whole grow stages in the pot. The first experiment was hydroponic experiment using twelve rice genotypes which were growth in the Yoshida Solution with addition of 0.2 % of agar. Three level of iron was given at 0, 500 and 700 ppm. The second experiment was the pot experiment using alluvial soil added with 3.000 ppm of ferrous combine with four levels of potassium and the control on Cilamaya Muncul (tolerant), Inpara 8 (moderate tolerant) and IR 64 (susceptible). In hydroponic experiment, even though the symptom appeared obviously, the leaf bronzing score (LBS) of tolerant and sensitive genotypes were not different. Physiological traits were significantly affected by Fe treatment in all varieties. Then symptom and physiological traits were significantly correlated. Through the pot experiment, it was confirmed the tolerance of each varieties. However, we couldn’t see the correlation between the LBS on hydroponic and soil at this time. And the heading delay was new finding, but it depended on varieties. We also could see the possibility of potassium application to inhibit iron toxicity but still we need to explore how it works. <br />Kata kunci: iron toxicity, rice, hydroponic, soil</p>