The physiological response of high Andean forest contrasting plants, Myrcianthes leucoxyla, a shadow-facultative heliophyte, and Abatia parviflora, a heliophyte, was studied during the transition from dry season to wet season in Bogotá. Light response curves (A-PAR), water potential (Ψw), transpiration rate (E), stomatal conductance (gs), leaf soluble protein content and peroxidase activity were measured in this study in a 48h cycle. The values for E, gs, Ψw and Ψw predawn for M. leucoxyla were 0.07 to 4.89 µg/cm s, 0.02 to 0.5 cm s-1, -0.025 to -1.05 MPa, and-0.1 MPa, respectively. For A. parviflora E, gs, Ψw and Ψw predawn were 0.47 to 12.27 µg/cm s, 0.17 to 1.42 cm s-1, -0.05 to -0.3 MPa and -0.075 MPa, respectively. A. parviflora presented a tendency of stomatal closure at midday and peroxidase activity increased with the increasing solar radiation, this did not occur in M. leucoxyla. The light compensation point (Ic) in A. parviflora was about 18.10 µmol photon m-2s-1, typical for a heliophyte plant; while for M. leucoxyla it was 8.87 µmol photon m-2s-1, slightly above the maximal reported values for shadow plants and under the minimal reported values for light plants. The lowest photosynthetic rate (A) of M. leucoxyla (2.8 µmol CO2 m-2s-1) in comparison with A. parviflora (7.4 µmol CO2 m-2s-1) is compensated with a better photonic use efficiency (± 0.7792 mol C mol-1).
A-PAR curves; Gas exchange; Heliophyte; Shadow plant; Water potential
