How does a C3 epiphytic tank bromeliad respond to drought?

Intermittent water availability characterizes the canopy habitat, but few studies have focused on how C3 epiphytic bromeliads deal with drought. In this context, we investigated how water deficits affect the photosynthetic responses of the epiphytic bromeliad Vriesea gigantea regarding its physiological and anatomical traits that can minimize the effects of stomatal closure. In a controlled experiment in which bromeliads were submitted to 21 days of drought, we demonstrated a reduction in the leaf water content followed by strong reductions in net CO2 exchange and the efficiency of the photochemical system. However, there were increases in the yield of non-photochemical quenching and the activities of hydrophilic antioxidants. We observed substomatal chambers connected with air channels reaching the chlorophyllous parenchyma. Our findings indicate that the low net CO2 exchange and the energy imbalance possibly increased the cyclic transport of electrons and activated the thermal dissipation of energy to avoid damage to the photosynthetic apparatus. Additionally, the aeration channels may passively store CO2 to facilitate its re-assimilation. Because most epiphytic bromeliads are C3 plants and drought is frequent in the canopy, we speculate that some attributes of V. gigantea may occur in other C3 species, favouring their radiation in the epiphytic environment.