The responses of photosynthetic gas exchange and chlorophyll a fluorescence to changes of irradiance and temperature in two species of Miscanthus

Photosynthetic CO2 uptake and chlorophyll (Chl) a fluorescence of C-4 perennial grasses, Miscanthus floridulus (Labill) Warb and M. transmorrisonensis Hayata, from altitudes in central Taiwan of 390 and 2700 m, respectively, were studied at 10 and 25 degrees C to find if the species differ in their photosynthetic responses to a low temperature, and whether their photosystems 2 become more susceptible to the photoinhibition at low temperatures. For both species, the maximum photosynthetic rate (P-max) was reduced when the leaves were exposed to 10 degrees C. At irradiances higher than 400 mu mol m(-2) s(-1), the values of F-v/F-m were reduced in both species at 10 degrees C but not at 25 degrees C, which indicated the photoinhibition at 10 degrees C. Reductions in P and the values of F-v/F-m at 10 degrees C were lesser in M. transmorrisonensis than in M. floridulus.