Watkins, Jr., James E. , Holbrook, Noel , Zwieniecki, Maciej A. .
Loss of leaf hydraulic function in gas exchange of epiphytic ferns: consequences for pteridophtye evolution.
Water availability is one of the most important aspects shaping plant distributions. As such, it is not surprising that plants have evolved sophisticated water delivery systems to ensure that water is transported both safely and efficiently. In contrast to most angiosperms, ferns rely on a relatively primitive tracheid based transport system. We have previously shown that, when compared to seed plants, ferns are hydraulically compromised and have significantly greater resistance to water flow in their xylem. Within the ferns, hydraulic conductivity is closely related to life form with epiphytic taxa exhibiting significantly lower conductivity compared to terrestrial taxa. The goal of the present study was to understand better how such hydraulic properties influence leaf level gas exchange. We examined a diverse assemblage of tropical ferns to: 1) understand how leaf and xylem specific hydraulic conductivity influence maximum photosynthetic and transpiration rates and 2) to understand how these traits influence species distributions. We found that, when viewed as a composite, there was a significant correlation between maximum photosynthetic and transpiration rates with leaf specific conductivity. However, when ferns were separated into epiphytic and terrestrial life forms such relationships only held for terrestrial but not epiphytic taxa. These results, combined with our previous work, suggest that two fundamentally different ecophysiological trajectories have evolved in the ferns.
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1 - Colgate University, Biological Sciences, 13 Oak Drive, Hamilton, New York, 13346, USA
2 - Harvard University, Organismic and Evolutionary Biology
3 - Harvard University, Arnold Arboretum, 16 Divinity Ave., Cambridge, MA, 02138, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 28th, 2008
Time: 9:00 AM