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Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores
Grasses have been considered to primarily employ tolerance in lieu of defense in mitigating damage caused by herbivory. Yet a number of mechanisms have been identified in grasses, which may deter feeding by grazers. These include enhanced silicon uptake, hosting of toxin-producing endophytic fungi a...
Autores principales: | , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Frontiers Media S.A.
2014
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4166226/ https://www.ncbi.nlm.nih.gov/pubmed/25278951 http://dx.doi.org/10.3389/fpls.2014.00478 |
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author | Huitu, Otso Forbes, Kristian M. Helander, Marjo Julkunen-Tiitto, Riitta Lambin, Xavier Saikkonen, Kari Stuart, Peter Sulkama, Sini Hartley, Sue |
author_facet | Huitu, Otso Forbes, Kristian M. Helander, Marjo Julkunen-Tiitto, Riitta Lambin, Xavier Saikkonen, Kari Stuart, Peter Sulkama, Sini Hartley, Sue |
author_sort | Huitu, Otso |
collection | PubMed |
description | Grasses have been considered to primarily employ tolerance in lieu of defense in mitigating damage caused by herbivory. Yet a number of mechanisms have been identified in grasses, which may deter feeding by grazers. These include enhanced silicon uptake, hosting of toxin-producing endophytic fungi and induction of secondary metabolites. While these mechanisms have been individually studied, their synergistic responses to grazing, as well as their effects on grazers, are poorly known. A field experiment was carried out in 5 × 5 m outdoor enclosures to quantify phytochemical changes of either endophyte-infected (E+) or endophyte-free (E-) meadow fescue (Schedonorus pratensis) in response to medium intensity (corresponding with densities of ca. 1200 voles/ha for 5 weeks during 3 months) or heavy intensity (ca. 1200 voles/ha for 8 weeks during 3 months) grazing by a mammalian herbivore, the field vole (Microtus agrestis). A laboratory experiment was then conducted to evaluate the effects of endophyte infection status and grazing history of the grass diet on vole performance. As predicted, grazing increased foliar silicon content, by up to 13%. Grazing also increased foliar levels of phosphorous and several phenolic compounds, most notably those of the flavonols isorhamnetin-diglycoside and rhamnetin derivative. Silicon concentrations were consistently circa 16% higher in E+ grasses than in E-grasses, at all levels of grazing. Similarly, concentrations of chlorogenic acid derivative were found to be consistently higher in E+ than in E- grasses. Female voles maintained on heavily grazed grasses suffered higher mortality rates in the laboratory than female voles fed ungrazed grass, regardless of endophyte infection status. Our results conclusively demonstrate that, in addition to tolerance, grasses employ multi-tiered, effective defenses against mammalian grazers. |
format | Online Article Text |
id | pubmed-4166226 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2014 |
publisher | Frontiers Media S.A. |
record_format | MEDLINE/PubMed |
spelling | pubmed-41662262014-10-02 Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores Huitu, Otso Forbes, Kristian M. Helander, Marjo Julkunen-Tiitto, Riitta Lambin, Xavier Saikkonen, Kari Stuart, Peter Sulkama, Sini Hartley, Sue Front Plant Sci Plant Science Grasses have been considered to primarily employ tolerance in lieu of defense in mitigating damage caused by herbivory. Yet a number of mechanisms have been identified in grasses, which may deter feeding by grazers. These include enhanced silicon uptake, hosting of toxin-producing endophytic fungi and induction of secondary metabolites. While these mechanisms have been individually studied, their synergistic responses to grazing, as well as their effects on grazers, are poorly known. A field experiment was carried out in 5 × 5 m outdoor enclosures to quantify phytochemical changes of either endophyte-infected (E+) or endophyte-free (E-) meadow fescue (Schedonorus pratensis) in response to medium intensity (corresponding with densities of ca. 1200 voles/ha for 5 weeks during 3 months) or heavy intensity (ca. 1200 voles/ha for 8 weeks during 3 months) grazing by a mammalian herbivore, the field vole (Microtus agrestis). A laboratory experiment was then conducted to evaluate the effects of endophyte infection status and grazing history of the grass diet on vole performance. As predicted, grazing increased foliar silicon content, by up to 13%. Grazing also increased foliar levels of phosphorous and several phenolic compounds, most notably those of the flavonols isorhamnetin-diglycoside and rhamnetin derivative. Silicon concentrations were consistently circa 16% higher in E+ grasses than in E-grasses, at all levels of grazing. Similarly, concentrations of chlorogenic acid derivative were found to be consistently higher in E+ than in E- grasses. Female voles maintained on heavily grazed grasses suffered higher mortality rates in the laboratory than female voles fed ungrazed grass, regardless of endophyte infection status. Our results conclusively demonstrate that, in addition to tolerance, grasses employ multi-tiered, effective defenses against mammalian grazers. Frontiers Media S.A. 2014-09-17 /pmc/articles/PMC4166226/ /pubmed/25278951 http://dx.doi.org/10.3389/fpls.2014.00478 Text en Copyright © 2014 Huitu, Forbes, Helander, Julkunen-Tiitto, Lambin, Saikkonen, Stuart, Sulkama and Hartley. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms. |
spellingShingle | Plant Science Huitu, Otso Forbes, Kristian M. Helander, Marjo Julkunen-Tiitto, Riitta Lambin, Xavier Saikkonen, Kari Stuart, Peter Sulkama, Sini Hartley, Sue Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores |
title | Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores |
title_full | Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores |
title_fullStr | Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores |
title_full_unstemmed | Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores |
title_short | Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores |
title_sort | silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores |
topic | Plant Science |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4166226/ https://www.ncbi.nlm.nih.gov/pubmed/25278951 http://dx.doi.org/10.3389/fpls.2014.00478 |
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