Crassulacean acid metabolism,CO2-recycling,and tissue desiccation in the Mexican epiphyte Tillandsia schiedeana Steud (Bromeliaceae)

After 23 days without water in a greenhouse, rates of nocturnal CO₂ uptake in Tillandsia schiedeana decreased substantially and maximum rates occurred later in the dark period eventually coinciding with the onset of illumination. Nocturnal CO₂ uptake accounted for less than half the total nighttime increase in acidity measured in well-watered plants. With increased tissue desiccation, only 11–12% of measured acid accumulation was attributable to atmospheric CO₂ uptake. Plants desiccated for 30 days regained initial levels of nocturnal acid accumulation and CO₂ uptake after rehydration for 10h. These results stress the importance of CO₂ recycling via CAM in this epiphytic bromeliad, especially during droughts.Partially supported by Biomedical Sciences Support Grant RR07037.