In the tropical forest of Barro Colorado Island, habitat characteristics, diel acidity changes, CO2 uptake and growth were investigated for the epiphytic cactus Epiphyllum phyllanthus (L.) Haw. It occurred most frequently in tree cavities with its roots in canopy soil and was especially abundant on two tree species: Platypodium elegans J. Vogel and Tabebuia guayacan (Seem.) Hemsl. Its maximum net CO2 uptake rates were low under natural conditions (1.4 μmol m−1) but were comparable to those of other CAM and C3 epiphytes under wet conditions in a screenhouse. Under both natural conditions and in the screenhouse, partial shade enhanced growth and CAM activity. When plants grew under a photosynthetic photon flux of c. 4 mol m−2 d−1, their nocturnal acidity increase and total net CO2 uptake were twice as much as for plants growing at lower (an average of 2.4 mol m−2 d−1) and higher (7.7 mol m−2 d−1) photosynthetic photon fluxes. Stem elongation was 27% greater at the intermediate photosynthetic photon flux. Seedlings of E. phyllanthus survived three months of drought and responded rapidly to rewetting, recovering fully within three days. Transpiration rates and nocturnal acidity increases also recovered to the values of well-watered plants a few days after rewetting, indicating that this species can take advantage of episodic rainfall during the dry season.

Dew deposition was calculated for leaves of the epiphytic bromeliads Tillandsia brachycaulos and T. elongata in a tropical dry deciduous forest in Yucatán, Mexico, over one year. Plant characteristics and water relations were also measured. Estimations were made by using energy balance analysis and the Penman–Monteith equation. Dew accumulation was also quantified using a cloth-plate method and by change in mass of whole plants. Tissue water content and total leaf area were similar in the two species, but maximum tank water content was three-fold greater for T. elongata than for T. brachycaulos, which had a lower degree of tissue desiccation tolerance than T. elongata. Succulence for T. brachycaulos changed little during most of the year, decreasing significantly only during one month in the dry season. Leaf water potential and osmotic pressure did not change significantly after a dew-deposition event. Theoretical dew per night on leaves was greatest during the early dry season (about 0.72 mm) compared with 0.34 mm in the rainy season and 0.008 mm in the late dry season. Dew amounts alone are not adequate to support growth but may maintain a favourable water balance for epiphytic bromeliads during the driest months of the year.