Fig 2. Photosynthetic efficiency of Bracken and Setaria under field conditions.

CO₂-assimilation rates (A) of both species were measured in the field at 1835 m a.s.l. (site 1, gray bars) and 2110 m a.s.l. (site 2, white bars). A was determined under physiologically relevant conditions of the study site at light intensities of 1200 μmol quanta m^-2 s^-1, internal CO₂ concentrations of 200 μmol CO₂ mol^-1 and 25°C. The graph shows the mean ±SEM (n ≥3). According to the Student t-test, the differences between all A values are significant (p ≤ 0.01).