Nerg Anne-Marja, Kasurinen Anne, Holopainen Toini, Julkunen-Tiitto Riitta, Neuvonen Seppo, Holopainen Jarmo K
Department of Environmental Science, University of Kuopio, Kuopio, Finland.
J Chem Ecol. 2008 Oct;34(10):1322-30. doi: 10.1007/s10886-008-9542-z. Epub 2008 Sep 17.
We tested whether the ectomycorrhizal (ECM) infection level of roots of silver birch (Betula pendula) affects performance of above-ground insect herbivores by increasing available plant biomass, by enhancing availability of nutrients, or by modifying concentration of defense compounds, i.e., phenolics, in birch foliage. Insect performance was determined for a phloem-feeding generalist (Lygus rugulipennis, the European tarnished plant bug), a phloem-feeding specialist (Calaphis flava, the birch aphid), and a chewing generalist (Epirrita autumnata, the autumnal moth larva). Silver birch plantlets had either natural ECM infection level (on average 24% of short roots with ECM), reduced ECM infection level with fungicide (F-, 9% ECM), or enhanced ECM infection level after inoculation with the fungus Paxillus involutus (PI+, 45% ECM) or Leccinum versipelle (LV+, 42% ECM). In general, the most pronounced effect of ECM was observed on growth of plantlets, i.e., stem growth decreased. In PI+-treated plants, leaf biomass also decreased. The effect of mycorrhizal colonization on the host plant's nitrogen (N) and phosphorous (P) concentration was dependent on the mycorrhizal species and experiment. Fungicide treatment did not cause a consistent decrease in nutrients. Finally, defense of birch against herbivory, expressed as foliar phenolic concentration in plantlets, was not modified by ECM. However, E. autumnata had a significantly higher relative growth rate on PI+ plantlets with high leaf N concentration than on LV+ plantlets with low leaf N concentration. The birch aphid C. flava produced significantly less nymphs on birches with enhanced ECM infection levels (PI+ and LV+ plantlets) than on controls. In summary, our data show that the ECM infection level mainly affects the growth parameters of plantlets, whereas effects on leaf chemical quality are minor. Our data show that effects of ECM infection of birch roots on aboveground herbivores are multifaceted and depend on the fungal species forming ectomycorrhiza and also on the degree of specialization and feeding guild of insects.
我们测试了白桦（Betula pendula）根系的外生菌根（ECM）感染水平是否通过增加可利用的植物生物量、提高养分有效性或改变白桦叶片中防御化合物（即酚类物质）的浓度来影响地上食草昆虫的表现。我们测定了一种取食韧皮部的多食性昆虫（Lygus rugulipennis，欧洲牧草盲蝽）、一种取食韧皮部的专食性昆虫（Calaphis flava，桦蚜）和一种咀嚼式多食性昆虫（Epirrita autumnata，秋尺蠖幼虫）的表现。白桦幼苗的ECM感染水平分为自然感染水平（平均24%的短根带有ECM）、用杀菌剂降低ECM感染水平（F-，9% ECM），或接种真菌卷缘桩菇（PI+，45% ECM）或疣柄牛肝菌（LV+，42% ECM）后提高ECM感染水平。总体而言，观察到ECM对幼苗生长的影响最为显著，即茎生长减少。在PI+处理的植株中，叶片生物量也有所下降。菌根定殖对宿主植物氮（N）和磷（P）浓度的影响取决于菌根种类和实验。杀菌剂处理并未导致养分持续减少。最后，白桦对食草动物的防御，以幼苗叶片酚类物质浓度表示，并未因ECM而改变。然而，秋尺蠖在叶片N浓度高的PI+幼苗上的相对生长速率显著高于叶片N浓度低的LV+幼苗。桦蚜在ECM感染水平增强的白桦（PI+和LV+幼苗）上产生的若虫明显少于对照组。总之，我们的数据表明，ECM感染水平主要影响幼苗的生长参数，而对叶片化学质量的影响较小。我们的数据表明，白桦根的ECM感染对地上食草动物的影响是多方面的，取决于形成外生菌根的真菌种类，也取决于昆虫的专业化程度和取食类群。
