Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores.
Silicon, endophytes and secondary metabolites as grass defenses against mammalian herbivores.
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DOI：
10.3389/fpls.2014.00478
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发表时间：
2014
影响因子：
5.6
通讯作者：
Hartley S
中科院分区：
文献类型：
--
作者：
Huitu O;Forbes KM;Helander M;Julkunen-Tiitto R;Lambin X;Saikkonen K;Stuart P;Sulkama S;Hartley S
在减轻草食造成的损害方面，禾本科植物被认为主要是采用耐受性而不是防御性。然而，在草类中已经发现了一些机制，这些机制可能会阻止食草动物的进食。这些包括增强硅吸收，寄主产生毒素的内生真菌和诱导次生代谢物。虽然这些机制已经被单独研究过，但它们对放牧的协同反应以及它们对食草动物的影响却知之甚少。在5 × 5 m的室外围栏中进行了野外实验，以量化受内生菌感染（E+）或无内生菌（E-）草甸羊茅（Schedonorus pratensis）在中等强度（相当于3个月内约1200只田鼠/公顷，持续5周）或重度（相当于3个月内约1200只田鼠/公顷，持续8周）放牧下的植物化学变化。通过室内实验，研究了草食饲史和内生菌感染状况对田鼠生产性能的影响。正如预测的那样，放牧使叶片硅含量增加了13%。放牧也增加了叶片磷和几种酚类化合物的含量，最显著的是黄酮醇异鼠李苷二糖苷和鼠李素衍生物。在所有放牧水平下，E+草的硅浓度始终比E+草高16%左右。同样，绿原酸衍生物的浓度在E+草中始终高于E-草。在实验室中，无论内生菌感染状况如何，饲喂重度放牧草地的雌性田鼠的死亡率高于饲喂未放牧草地的雌性田鼠。我们的研究结果最终表明，除了耐受性外，草类对哺乳动物食草动物还采取了多层有效的防御措施。
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.
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影响因子：
6.6
作者：
Conover, MR
通讯作者：
Conover, MR
影响因子：
3.4
作者：
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作者：
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