title: Effects of Irradiance on Crassulacean Acid Metabolism in the Epiphyte Tillandsia usneoides L. (Bromeliaceae).
abstract: Spanish moss (Tillandsia usneoides L.) was collected in South Carolina, maintained in a greenhouse, then exposed to five levels of photosynthetic photon flux density (PPFD) for 3 weeks. Following this treatment, plants were sampled for chlorophyll concentrations, nocturnal acid accumulations, and photosynthetic responses to subsequent exposure at a range of PPFD. No acclimation to PPFD was observed; all plants exhibited similar patterns of nocturnal CO(2) uptake and acid accumulation regardless of initial PPFD treatment. These patterns revealed that at a PPFD level of approximately 200 micromoles per square meter per second (daytime integrated PPFD of 10 moles per square meter per day), CAM saturated or, in low-PPFD plants, was optimal. The results of this study indicate that adaptation to high PPFD is not necessarily a requirement of CAM.
authors: Department of Botany, University of Kansas, Lawrence, Kansas 66045.
authors: C E
authors: CE
authors: Martin
authors: C A
authors: CA
authors: Eades
authors: R A
authors: RA
authors: Pitner