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...
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| Format: | Article |
| Language: | English |
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Frontiers Media S.A.
2014-09-01
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| Series: | Frontiers in Plant Science |
| Subjects: | |
| Online Access: | http://journal.frontiersin.org/Journal/10.3389/fpls.2014.00478/full |
| _version_ | 1819327168793018368 |
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| author | Otso eHuitu Kristian eForbes Marjo eHelander Riitta eJulkunen-Tiitto Xavier eLambin Kari eSaikkonen Peter eStuart Sini eSulkama Sue Elaine Hartley |
| author_facet | Otso eHuitu Kristian eForbes Marjo eHelander Riitta eJulkunen-Tiitto Xavier eLambin Kari eSaikkonen Peter eStuart Sini eSulkama Sue Elaine Hartley |
| author_sort | Otso eHuitu |
| collection | DOAJ |
| 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. |
| first_indexed | 2024-12-24T13:06:33Z |
| format | Article |
| id | doaj.art-4d1e9e80d49d4a0790aedf60cbed9c21 |
| institution | Directory Open Access Journal |
| issn | 1664-462X |
| language | English |
| last_indexed | 2024-12-24T13:06:33Z |
| publishDate | 2014-09-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Plant Science |
| spelling | doaj.art-4d1e9e80d49d4a0790aedf60cbed9c212022-12-21T16:53:59ZengFrontiers Media S.A.Frontiers in Plant Science1664-462X2014-09-01510.3389/fpls.2014.00478100750Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivoresOtso eHuitu0Kristian eForbes1Marjo eHelander2Riitta eJulkunen-Tiitto3Xavier eLambin4Kari eSaikkonen5Peter eStuart6Sini eSulkama7Sue Elaine Hartley8Finnish Forest Research InstituteFinnish Forest Research InstituteUniversity of TurkuUniversity of Eastern FinlandUniversity of AberdeenAgrifood Research FinlandFinnish Forest Research InstituteFinnish Forest Research InstituteUniversity of YorkGrasses 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.http://journal.frontiersin.org/Journal/10.3389/fpls.2014.00478/fullEndophytesSilicongrassesDefensegrazingphenolics |
| spellingShingle | Otso eHuitu Kristian eForbes Marjo eHelander Riitta eJulkunen-Tiitto Xavier eLambin Kari eSaikkonen Peter eStuart Sini eSulkama Sue Elaine Hartley Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores Frontiers in Plant Science Endophytes Silicon grasses Defense grazing phenolics |
| 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 | Endophytes Silicon grasses Defense grazing phenolics |
| url | http://journal.frontiersin.org/Journal/10.3389/fpls.2014.00478/full |
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