Using Phylogenetically Independent Contrasts to Examine Temperature Acclimation of Root and Mycorrhizal Fungal Respiration Among Organisms from Broad Latitudinal Gradients

在许多环境中，温度是菌根代谢的主要制约因素。在寒冷的气候中，春季的温度限制了根系的代谢和养分的获取。在温带和热带气候的夏季，未遮荫的土壤可能达到导致碳水化合物代谢过度的温度，除非根驯化发生。本提案的中心目标是研究原产地纬度如何影响植物根和菌根真菌对土壤温度的呼吸反应。这些研究人员将使用系统发育独立的对比（使用不同进化谱系的对比）来对植物和菌根真菌对温度的反应作为起源纬度的函数进行一般推断。这项研究将集中在与有机体对温度的反应有关的四个相互关联的假设上。昼夜温度的变化会影响生物体对温度的适应能力吗？在没有驯化的条件下，在相同温度下测量时，高纬度地区的植物和菌根真菌是否比低纬度地区的植物和菌根真菌表现出更高的呼吸作用？在发生驯化的条件下，高纬度地区的植物和菌根真菌对高温的驯化（即过度代谢碳水化合物）是否比低纬度地区的植物和菌根真菌表现得更差？独立的菌根真菌或植物对温度的呼吸反应在共生中是否相同？利用真菌和植物的多种不同进化谱系，将为了解生物如何在全球范围内对平均温度和温度变化做出反应提供新的见解。这项工作有几个机会产生更广泛的科学影响。全球气候变化是科学家和政府决策者都非常感兴趣的一个领域。政府间气候变化专门委员会预测，到2100年，全球地表温度将上升1.4-5.8摄氏度。该委员会使用的大气模型假设大气中二氧化碳的增加将导致环境温度升高，从而增加土壤呼吸，从而产生正反馈。在许多土壤中，菌根呼吸是土壤呼吸的主要来源。如果菌根适应了温度的升高，那么预测的地表温度的升高可能被高估了。还将有几个机会加强科学培训。在本科阶段，学生将以几种有意义的方式参与该项目，包括学习如何培养菌根真菌并评估其在根上的定植，种植植物以及使用气体交换系统测量根和真菌的呼吸作用，这需要了解数据记录仪，气体分析仪，气体流量计和控制器。博士后还将有机会接受根和菌根真菌生理学的培训，并与一名外国研究生一起参加波兰的实地研究项目。

Temperature is a major constraint on mycorrhizal root metabolism in many environments. In cold climates, temperatures in the spring restrict root metabolism and nutrient acquisition. In the summer in temperate and tropical climates, unshaded soils may reach temperatures that cause excessive carbohydrate metabolism unless root acclimation occurs. The central objective of this proposal is to examine how latitude of origin affects plant root and mycorrhizal fungal respiratory responses to soil temperature. These investigators will use phylogenetically independent contrasts (contrasts using distinct evolutionary lineages) to permit general inferences on plant and mycorrhizal fungal responses to temperature as a function of latitude of origin. The research will focus on four, interrelated hypotheses associated with organism response to temperature. Does diurnal temperature variation affect an organism's ability to acclimate to temperature? Under conditions of no acclimation, do plants and mycorrhizal fungi from higher latitudes exhibit higher respiration than those from lower latitudes when measured at the same temperature? Under conditions where acclimation occurs, do plants & mycorrhizal fungi from high latitudes exhibit less acclimation to high temperature (i.e., excessively metabolize carbohydrates) than those from lower latitudes? Are the independent mycorrhizal fungal or plants respiratory responses to temperature the same when the organisms are measured in symbiosis? The use of multiple, distinct evolutionary lineages of both fungi and plants will provide new insight into how organisms respond globally to both average temperatures and temperature variation.This work has several opportunities for broader scientific impacts. Global climate change is an area of intense interest to both scientists and government policy makers. The Intergovernmental Panel on Climate Change predicts a 1.4-5.8 degree C increase in global surface temperature by 2100, using atmospheric models that assume increases in atmospheric CO2 will lead to increases in ambient temperature, which increases soil respiration, causing a positive feedback. Mycorrhizal root respiration represents the dominant source of soil respiration in many soils. If mycorrhizal roots acclimate to increases in temperature, than predicted increases in surface temperatures may be overestimated. There will also be several opportunities to enhance scientific training. At the undergraduate level, students will be involved in the project in several meaningful ways, including learning how to culture mycorrhizal fungi and assess their colonization on roots, growing plants and measuring the respiration of roots and fungi using a gas-exchange system that requires an understanding of data loggers, gas analyzers and gas flow meters and controllers. The postdoctoral fellow will also have opportunities to become trained both in root and mycorrhizal fungal physiology and participate in a field project with a foreign graduate student in Poland.