Journal Article

Structure-function constraints of tracheid-based xylem: a comparison of conifers and ferns

Rico, Christopher, Christman, Mairgareth A., Limm, Emily, Pittermann, Jarmila

2011

Overview

The ferns comprise one of the most ancient tracheophytic plant lineages, and occupy habitats ranging from tundra to deserts and the equatorial tropics. Like their nearest relatives the conifers, modern ferns possess tracheid-based xylem but the structure-function relationships of fern xylem are poorly understood. Here, we sampled the fronds (megaphylls) of 16 species across the fern phylogeny, and examined the relationships among hydraulic transport, drought-induced cavitation resistance, the xylem anatomy of the stipe, and the gas-exchange response of the pinnae. For comparison, the results are presented alongside a similar suite of conifer data. Fern xylem is as resistant to cavitation as conifer xylem, but exhibits none of the hydraulic or structural trade-offs associated with resistance to cavitation. On a conduit diameter basis, fern xylem can exhibit greater hydraulic efficiency than conifer and angiosperm xylem. In ferns, wide and long tracheids compensate in part for the lack of secondary xylem and allow ferns to exhibit transport rates on a par with those of conifers. We suspect that it is the arrangement of the primary xylem, in addition to the intrinsic traits of the conduits themselves, that may help explain the broad range of cavitation resistance in ferns.

• Publisher: John Wiley & Sons,Blackwell Publishing Ltd
• Subject: anatomy & histology / Angiospermae / Angiosperms / Biological Evolution / Biological Transport / cavitation / Cavitation flow / Coniferophyta - anatomy & histology / Coniferophyta - physiology / Conifers / Dehydration / Dehydration - genetics / Dehydration - physiopathology / deserts / Evolution / Ferns / Ferns - anatomy & histology / Ferns - physiology / ferns and fern allies / gas exchange / genetics / habitats / hydraulic conductivity / Hydraulics / phylogeny / physiology / physiopathology / Plant Stems / Plant Stems - anatomy & histology / Plant Stems - physiology / Plant Transpiration / Plants / primary xylem / secondary xylem / sporophytes / Structure-Activity Relationship / structure-activity relationships / Tracheids / Tracheophyta / tropics / tundra / Water transportation / Xylem / Xylem - anatomy & histology / Xylem - physiology / xylem evolution