Physiology and genetics of nitrogen uptake and metabolism in trees

植物面临着扎根的独特挑战。它们必须在整个生命周期中从有限的土壤中获取养分--就树木而言，需要几个世纪。在加拿大，森林土壤通常是寒冷，酸性和低的有效养分，特别是氮（N）。了解树木对这些土壤的适应性，以及这些土壤如何塑造树木对气候变化的反应，是一个重要的实践和科学目标。在自然系统中，树根与真菌伙伴，真菌，这是至关重要的营养矿化，吸收和转移到主机。不同的菌根物种在它们的能力，以打破有机质和养分，并在他们对非生物因素的反应。这对气候变化中的树木营养具有重要意义。我们对真菌之间的变异以及温度或CO2对这些共生体的影响知之甚少。该提案描述了一个程序的研究树根及其相关的菌根真菌，以及这些共生体的影响，对氮的吸收和N-形式的偏好，对比温度，氮的可用性和CO2。在这个项目中以前的研究集中在树木根系的N吸收，单独。我们已经记录了物种间和物种内营养吸收和利用效率的遗传变异，并发现土壤温度影响氮的吸收形式。随着全球气温上升，这些影响将对森林生长和群落结构产生重大影响。未来的研究将调查对比树和菌根物种，以了解根温如何影响细胞和全根水平的氮吸收速率和形式，氮吸收基因的表达，以及CO2如何影响树和真菌之间的氮碳平衡。这项工作将加深我们对菌根共生体功能多样性的理解，并将揭示森林对全球变化反应的潜在复杂性。该研究旨在培训五名研究生和一些本科生，他们将成为NSERC森林和气候变化CREATE计划的一部分。

Plants face the unique challenge of being rooted in place. They must acquire nutrients from a limited volume of soil over an entire lifetime - in the case of trees, over centuries. In Canada, forest soils are typically cold, acidic and low in available nutrients, particularly nitrogen (N). Understanding the adaptations of trees to these soils, and how these may shape tree response to changing climates is an important practical and scientific goal. In natural systems, tree roots associate with fungal partners, mycorrhizae, that are vital to nutrient mineralization, uptake and transfer to the host. Mycorrhizal species differ in their ability to break down organic matter and take up nutrients, and in their response to abiotic factors. This has important implications for tree nutrition in changing climates. We know little about variation among mycorrhizae or about the effects of temperature or CO2 on these symbioses. This proposal describes a program of research on tree roots and their associated mycorrhizal fungi, and the effects of these symbioses on N uptake and N-form preference under contrasting temperatures, N availability and CO2. Previous research in this program has focused on N uptake by tree roots, alone. We have documented genetic variation among and within species in nutrient uptake and use efficiency, and found that soil temperature affects the form in which N is taken up. As global temperatures rise, these effects will have significant implications for forest growth and community structure. Future research will investigate contrasting tree and mycorrhizal species to understand how root temperature affects the rate and form of N uptake at the cellular and whole-root level, the expression of genes integral to N uptake, and how CO2 affects the N-carbon balance between the tree and fungus. This work will deepen our understanding of the functional diversity in mycorrhizal symbioses, and will reveal potential complexities in forest response to global change. The research is designed for the training of five graduate students and a number of undergraduates who will be part of the NSERC CREATE Program in Forests and Climate Change.