Abstract: Using the method of Open-top chambers (OTC) to simulate climate warming in the future, The study was carried out in reclaimed marsh in Eastern Chongming Island in rapid growth season. The results showed that the net photosynthetic rate(〖WTBX〗Pn〖WTBZ〗), transpiration rate(〖WTBX〗Tr〖WTBZ〗) and stomatal conductance(〖WTBX〗Gs〖WTBZ〗) of 〖WTBX〗P. australis 〖WTBZ〗in OTC were significantly reduced by 11.9%, 22.5% and 21.7%, respectively, while the intercellular CO2 concentration(〖WTBX〗Ci〖WTBZ〗) and water use efficiency (〖WTBX〗WUE)〖WTBZ〗 were lower, but the changes were not significant. The net photosynthetic rate-light intensity (〖WTBX〗Pn-PAR〖WTBZ〗) curves which were nonlinear fitted in OTC and CK showed the same trend that Pn increased quickly and then hasten gentle by 〖WTBX〗PAR〖WTBZ〗. In OTC, photosynthetic response curve of the 〖WTBX〗P. australis〖WTBZ〗 was lower than the control plots; at the same time, the temperature enhancement made the light saturation point (〖WTBX〗LSP〖WTBZ〗) and apparent quantum efficiency (〖WTBX〗AQY〖WTBZ〗) dramatically reduced by 22.0% and 12.1%, respectively, but the dark respiration rate (〖WTBX〗Rd〖WTBZ〗) and light compensation point (〖WTBX〗LCP〖WTBZ〗) respectively increased by 16.5% and 14.9%. The maximum net photosynthetic rate(〖WTBX〗P〖WTBZ〗max) of 〖WTBX〗P. australis〖WTBZ〗 in OTC was not evidently effected. Meanwhile, the leaf nitrogen content(〖WTBX〗N〖WTBZ〗mass) of 〖WTBX〗P. australis 〖WTBZ〗in OTC were significantly reduced, while the leaf mass per area (〖WTBX〗LMA 〖WTBZ〗) was higher, but the changes of photosynthetic nitrogen use efficiency (〖WTBX〗PNUE〖WTBZ〗) was not significant. To 〖WTBX〗P. australis〖WTBZ〗 in Eastern Chongming Island, the 〖WTBX〗LMA 〖WTBZ〗was significantly negatively correlated with the 〖WTBX〗PNUE〖WTBZ〗 ,〖WTBX〗P〖WTBZ〗mass (〖WTBX〗p〖WTBZ〗 ≤0.05) and 〖WTBX〗N〖WTBZ〗mass(〖WTBX〗p〖WTBZ〗 ≤0.01), while the 〖WTBX〗Nmass〖WTBZ〗 was positively correlated with the 〖WTBX〗PNUE〖WTBZ〗(〖WTBX〗p 〖WTBZ〗≤0.01) . The correlation analysis showed that the 〖WTBX〗P〖WTBZ〗max was significantly positively correlated with 〖WTBX〗N〖WTBZ〗mass(〖WTBX〗p 〖WTBZ〗≤0.01) and 〖WTBX〗PNUE(p〖WTBZ〗≤0.05〖WTBX〗).〖WTBZ〗In summary, the simulated warming significantly affected the photosynthetic characteristics of 〖WTBX〗P. australis.

Key words: temperature enhancement, Phragmites australis, photosynthetic characteristics, factors