Recent Topics Posters
North, Gretchen , Phillips, Carly , Woodside, Walter .
Leaves of tank bromeliads: water supply and demand.
For tank bromeliads, the leaf is both the major supplier and consumer of water. Our goal was to understand how water supply and demand in this group are linked via leaf hydraulics. We investigated the hydraulic capacity of several species of tank bromeliad that occur in the neotropical wet forest, specifically, at La Selva Biological Station in Costa Rica, and whether differences in light environment and photosynthetic pathway are related to differences in leaf hydraulics. Species investigated were Aechmea nudicaulis, which is CAM; Guzmania monostachia, a C3-CAM intermediate; and Werhauia gladioliflora,a C3 species. Plants were examined at different heights in the canopy, made possible by the fall of three large host trees from which epiphytes were collected within 24 hours of tree-fall. We tested three hypotheses: 1) the CAM species A. nudicaulis would be the most prevalent higher in the canopy, followed by the CAM intermediate G. monostachia, 2) A. nudicaulis would be the most conservative of the three species with respect to leaf hydraulic supply, and 3) within species, those higher in the canopy would have greater leaf hydraulic conductivity. Hypothesis 1 was not supported in that the most abundant of the three species at the tops of the fallen trees (previously at 35-45 m in the canopy), was G. monostachia, followed by A. nudicaulis, with W. gladioliflora generally lowest. Whole plant and individual leaf area for plants collected from fallen host trees were separated into green blade area (transpiring area, or demand) and non-chlorophyllous leaf bases forming the tank (absorptive area, or supply). Hypothesis 2, that A. nudicaulis would be the most conservative of the species hydraulically, was supported, as the tank represented 57% of plant leaf area, followed by 37% for G. monostachia and 19% for W. gladioliflora. Individual leaf areas, leaf clearings, and leaf cross-sections were used to count the number of vascular bundles and measure tracheid diameters, which were used to calculate leaf hydraulic conductivity (kleaf; m2 MPa-1 s-1). Aechmea nudicaulis leaves from plants high in the canopy (40 m) had the highest kleaf, 2.09 E-08, followed by G. monostachia with 1.82 E-8 and W. gladioliflora with 7.94 E-9. Hypothesis 3 received some support in that kleaf for A. nudicaulis from 20 m in the canopy was 1.36 E-8. The CAM species thus had the greatest hydraulic capacity, although the C3-CAM intermediate was apparently the most successful at the greatest canopy heights.
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1 - Occidental College, 1600 CAMPUS RD, LOS ANGELES, CA, 90041, USA
2 - Occidental College, Biology, 1600 Campus Rd, Los Angeles, CA, 90041, USA
Presentation Type: Recent Topics Poster
Location: Khorassan Ballroom/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 5:30 PM