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

Abstract

Photosynthetic CO2 uptake and chlorophyll (Chl) a fluorescence of C4 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 °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 °C. At irradiances higher than 400 μmol m-2 s-1, the values of F(v)/F(m) were reduced in both species at 10 °C but not at 25 °C, which indicated the photoinhibition at 10 °C. Reductions in P(max) and the values of F(v)/F(m) at 10 °C were lesser in M. transmorrisonensis than in M. floridulus.