Ecophysiology of ectomycorrhizal symbioses

外生菌根是真菌与植物根系之间古老的共生关系。许多成员的松树，桦树，杨柳和山毛榉家庭严重依赖于这些真菌的合作伙伴充分吸收矿物质营养。在我的实验室里，我们研究了外生菌根真菌（EMF）的双重功能：作为共生体，可以将氮（N），磷（P）和其他矿物营养素转移到它们的植物伙伴中，作为土壤真菌，通过分泌降解酶，有助于土壤有机质的分解和碳（C），N，P和硫（S）的循环。由于EMF在植物养分吸收中起着重要作用，因此它们在树木应对环境变化的迁移或适应中将是重要的。我们计划调查是否不同的EMF社区使用不同的策略来获取P取决于类型的P（有机与无机），占主导地位的土壤中，他们被发现。如果EMF社区在当地适应，森林管理人员将需要管理的树木和EMF，如果重新种植计划改变了气候变化的结果。我的一个学生最近观察到一个主要的损失氮从松树幼苗时，他们的电磁场提供营养后，一段时间的饥饿。这表明N从幼苗转移到真菌，这与共生的传统理解相反。我们将测试这一假设的标签树叶，以及菌丝，与15 N和量化易位的N在两个方向使用质谱和复杂的显微镜方法。如果N从植物到EMF的运动得到证实，我们将与国际专家合作，研究N转运蛋白在菌根根真菌界面的行为。我们还将跟踪松树幼苗在田间和温室中的发芽和定植，看看我们是否可以检测到土壤养分状况突然变化后N运输方向的任何短期转变。这项研究将挑战传统观点的N运输外生菌根植物，特别是在幼苗建立，并增加了解N运输的菌根接口。虽然人们认为电磁场分解土壤有机质以获得N，P和S，但对于电磁场是否满足其对土壤C的任何C需求存在很大争议，因为它们可以直接获得最近固定在植物宿主根部的C。我们将在实验室中测试EMF的腐殖化行为，通过生长外生菌根松树与13C标记的土壤C。我们将通过分析EMF磷脂中的C同位素特征来量化从土壤与根部获得的C的比例。通过这项研究，并与国际合作者的参与，四个荣誉，三个硕士和两个博士生将接受培训，使用复杂的显微镜，同位素和分子技术，研究如何电磁场影响幼苗建立和营养循环在加拿大森林。

Ectomycorrhizae are ancient symbiotic relationships between fungi and plant roots. Many members of the pine, birch, willow and beech families depend heavily on these fungal partners for adequate uptake of mineral nutrients. In my lab, we look at the dual function of ectomycorrhizal fungi (EMF): as symbionts that can translocate nitrogen (N), phosphorus (P) and other mineral nutrients to their plant partners, and as soil fungi that, by excreting degradative enzymes, contribute to the breakdown of soil organic matter and the cycling of carbon (C), N, P and sulphur (S). Because EMF play a major role in plant nutrient uptake, they will be important in the migration or adaptation of trees in response to environmental change. We plan to investigate whether different EMF communities use different strategies for acquiring P depending on the types of P (organic vs inorganic) that dominant the soils in which they are found. If EMF communities are locally adapted, forest managers will need to manage both the trees and EMF if replanting programs are changed as a result of climate change. One of my students recently observed a major loss of N from pine seedlings when their EMF were supplied with nutrients after a period of starvation. This suggests that N moved from seedling to fungus, which is counter to conventional understanding of the symbiosis. We will test this hypothesis by labelling foliage, as well as hyphae, with 15N and quantify translocation of N in both directions using both mass spectrometry and sophisticated microscopic approaches. If movement of N from plant to EMF is confirmed, we will collaborate with an international expert to study behavior of N transporters at the root-fungal interface in mycorrhizal roots. We will also follow the germination and colonization of pine seedlings in the field and greenhouse to see if we can detect any short-term shift in the direction of N transport after a sudden change in soil nutrient status. This research will challenge the conventional view of N transport in ectomycorrhizal plants especially during seedling establishment, and increase understanding of N transport at the mycorrhizal interface. While it is accepted that EMF break down soil organic matter to access N, P and S, there is much debate about whether EMF meet any of their C needs from soil C, given that they have direct access to recently fixed C in roots of their plant hosts. We will test for saprotrophic behavior of EMF in the lab by growing ectomycorrhizal pine with 13C-labelled soil C. We will quantify the proportion of C acquired from soil vs roots by analyzing C isotope signatures in the phospholipids of the EMF. Through this research, and with the involvement of international collaborators, four honours, three MSc, and two PhD students will be trained in the use of sophisticated microscopic, isotopic and molecular techniques to study how EMF affect seedling establishment and nutrient cycling in Canadian forests.