24 - Are vessels in seed plants evolutionary innovations to similar ecological contexts?

Abstract

The ecological settings for vessel origins in seed plants need wider investigation today. Nevertheless, the hypothesis that vessels arose independently and under the similar circumstances of wet, shady conditions deserves further attention. In particular, additional functional studies, both of the fossils themselves and the extant products of these ancient radiations are needed. For instance, information on the comparative hydraulic properties of basal angiosperms, Gnetales, and gigantopterids is currently uninvestigated, which is necessary to test whether vessels in these groups are truly analogous. Using the excellent fossil record of gigantopterids, it may also be possible to make accurate inferences in physiologically important aspects of stem water transport (e.g., sapwood specific hydraulic conductivity and leaf area specific hydraulic conductivity). Comparative physiological work on basal angiosperms will be especially informative because the extant flora provides a continuum of xylem morphologies (from vesselless to large-diameter vessels with simple perforation plate) that occur in habitats differing primarily in light availability. This fortunate condition may allow piecing together how different patterns of vessel development drive hydraulic function.