Comparative photosynthesis of three gap phase successional tree species.

Photosynthesis was measured in situ on trees growing in an open, gap-like site and under a closed canopy. Photosynthetic responses also were monitored on trees grown in the laboratory under either a high or low light regime or on those trees transferred from a low to a high light regime. All three species studied, Liriodendron tulipifera, Acer rubrum and Cornus florida, were able to acclimate to a high light environment as evidenced by their higher photosynthetic rates. This acclimation was achieved by an increase in transfer conductance and was ultimately due to changes in leaf anatomy. Species avoided photo-bleaching primarily by changes in leaf orientation and canopy structure. Species-specific physiological responses to high light intensity may account for each species' known growth response following canopy opening.