April 27 2011

12:00 LSB 2320

Jarmila Pittermann
Dept of Ecology and Evolutionary Biology, UC Santa Cruz

The evolutionary eco-physiology of water transport in conifers and ferns.


In plants, water transport from soil to leaf occurs through the xylem under negative pressure or tension, which is generated by the evaporation of water from leaf cells. During drought periods when the tension in the water column is high, air can get sucked into the xylem and displace the water in the conduits rendering them embolized and thus hydraulically dysfunctional. In woody plants, water transport is governed by embolism-safety versus transport efficiency trade-offs that help us understand how natural selection drives the evolution of water transport. These generalizations were developed using conifers and woody angiosperms but do they apply to more primitive groups such as conifers and ferns? And if so, how? Unlike in angiosperms, in which water transport occurs through long, multi-cellular and hydraulically efficient vessels, ferns and conifers share single-celled tracheids as the fundamental vascular unit. However, conifers and ferns also exhibit profoundly different developmental patterns and vascular constraints. How efficient is water transport in ferns relative to conifers, how resistant is fern xylem to drought-induced embolism and do we see shared traits in these two groups that have been consistently selected for in modern plant vascular systems? My talk will explore the evolutionary structure-function trajectory of fern and conifer vascular systems in a modern and paleobotanical context.











































































































































































































































































































































































































































































































































































































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