Reasons for the presence or absence of convective (pressurized) ventilation in the genus Equisetum

Authors

  • Jean Armstrong,

    1. Department of Biological Sciences, University of Hull, Kingston upon Hull, HU6 7RX, UK and School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
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  • William Armstrong

    1. Department of Biological Sciences, University of Hull, Kingston upon Hull, HU6 7RX, UK and School of Plant Biology, Faculty of Natural and Agricultural Sciences, The University of Western Australia, 35 Stirling Highway, Crawley, WA 6009, Australia
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Author for correspondence:
Jean Armstrong
Tel: +44 1964 550135
Email: j.armstrong@hull.ac.uk

Summary

  • The very high rates of convective ventilation reported recently in Equisetum telmateia (up to 120 cm3 min−1; internal wind speed, 10 cm s−1) prompted this study of a further eight species for the presence or absence of convection and the possible reasons for this.
  • Convection rates were examined in relation to anatomical pathways, internal resistance to applied pressurized gas flow and stomata.
  • Only species with interconnecting cortical aerenchyma in branches (when present), shoots and rhizomes induced convection. Rapid humidity-induced convection (HIC) occurred in E. palustre (up to 13 cm3 min−1), with slower rates in E. × schaffneri and E. ramosissimum (≤ 6 and 3 cm3 min−1, respectively). Excised shoots of E. hyemale and E. fluviatile showed the potential for HIC (≤ 0.5 and 0.15 cm3 min−1, respectively), but not into the rhizomes. High rates were linked to low internal gas flow resistance. No convection was detected in E. scirpoides, E. sylvaticum or E. arvense due to the extremely high resistance to pressure flow, for example, from intercalary meristems and, in the last two, to nonaerenchymatous branches.
  • Of the nine Equisetum species studied so far, four showed through-flow convection; the other species must rely solely on diffusion for underground aeration in wet soils.

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