Klaus Mehltreter1,2, Hanna Wachter2, Christophe Trabi2, Weston Testo3,4, Michael Sundue5, Steven Jansen2. 1. Red de Ecología Funcional, Instituto de Ecología, A.C., Xalapa 91073, Veracruz, México. 2. Institute of Systematic Botany and Ecology, Ulm University, D-89081 Ulm, Germany. 3. Department of Biological and Environmental Sciences, University of Gothenburg, 40530 Goteborg, Sweden. 4. Botanical Research Institute of Texas, Fort Worth, TX 76107, USA. 5. The Pringle Herbarium, Department of Plant Biology, University of Vermont, Burlington, VT 05405, USA.
Abstract
BACKGROUND AND AIMS: Ferns are the second largest group of vascular plants and are distributed nearly worldwide. Although ferns have been integrated into some comparative ecological studies focusing on hydathodes, there is a considerable gap in our understanding of the functional anatomy of these secretory tissues that are found on the vein endings of many fern leaves. In this study, we aimed to investigate the phylogenetic distribution, structure and function of fern hydathodes. METHODS: We performed a global review on fern hydathodes and their phylogenetic distribution, carried out an ancestral character state reconstruction, and studied the structure, guttation and elemental composition of salt residues of eight species, and the diurnal patterns of xylem pressure of two species. KEY RESULTS: Hydathodes are known from 1189 fern species, 92 genera and 19 families of 2 orders, Equisetales and Polypodiales. Stochastic character mapping indicated multiple gains and losses of hydathodes at the genus level, occurring especially during the last 50 million years of fern evolution. Hydathodes were located on the adaxial leaf surface and characterized by a cytoplasm-rich, pore-free epidermis, and became functional for several weeks after nearly complete leaf expansion. In two species, positive xylem pressure built up at night, potentially facilitating guttation. Guttation fluid was rich in Ca and often Si, but also contained P, Mg, Na and Al. CONCLUSIONS: Stochastic character mapping and the structural and functional diversity of hydathodes indicate multiple origins, and their presence/absence in closely related taxa implies secondary losses during fern evolution. Positive xylem pressure and high air humidity play an important role as drivers of guttation. Hydathodes may contribute to the regulation of leaf nutrient stoichiometry by the release of excessive compounds and minerals other than waste products, but the presence of essential chemical elements in salt residues also indicates possible leakage.
BACKGROUND AND AIMS: Ferns are the second largest group of vascular plants and are distributed nearly worldwide. Although ferns have been integrated into some comparative ecological studies focusing on hydathodes, there is a considerable gap in our understanding of the functional anatomy of these secretory tissues that are found on the vein endings of many fern leaves. In this study, we aimed to investigate the phylogenetic distribution, structure and function of fern hydathodes. METHODS: We performed a global review on fern hydathodes and their phylogenetic distribution, carried out an ancestral character state reconstruction, and studied the structure, guttation and elemental composition of salt residues of eight species, and the diurnal patterns of xylem pressure of two species. KEY RESULTS: Hydathodes are known from 1189 fern species, 92 genera and 19 families of 2 orders, Equisetales and Polypodiales. Stochastic character mapping indicated multiple gains and losses of hydathodes at the genus level, occurring especially during the last 50 million years of fern evolution. Hydathodes were located on the adaxial leaf surface and characterized by a cytoplasm-rich, pore-free epidermis, and became functional for several weeks after nearly complete leaf expansion. In two species, positive xylem pressure built up at night, potentially facilitating guttation. Guttation fluid was rich in Ca and often Si, but also contained P, Mg, Na and Al. CONCLUSIONS: Stochastic character mapping and the structural and functional diversity of hydathodes indicate multiple origins, and their presence/absence in closely related taxa implies secondary losses during fern evolution. Positive xylem pressure and high air humidity play an important role as drivers of guttation. Hydathodes may contribute to the regulation of leaf nutrient stoichiometry by the release of excessive compounds and minerals other than waste products, but the presence of essential chemical elements in salt residues also indicates possible leakage.
Authors: Aude Cerutti; Alain Jauneau; Patrick Laufs; Nathalie Leonhardt; Martin H Schattat; Richard Berthomé; Jean-Marc Routaboul; Laurent D Noël Journal: Annu Rev Phytopathol Date: 2019-05-17 Impact factor: 13.078
Authors: Courtney E Campany; Jarmila Pittermann; Alex Baer; Helen Holmlund; Eric Schuettpelz; Klaus Mehltreter; James E Watkins Journal: Plant Cell Environ Date: 2021-03-18 Impact factor: 7.228
Authors: Helen I Holmlund; Stephen D Davis; Frank W Ewers; Natalie M Aguirre; Gerard Sapes; Anna Sala; Jarmila Pittermann Journal: J Exp Bot Date: 2020-01-23 Impact factor: 6.992