SGER: Using Stable Isotopes as Tracers to Measure Below Ground Neighborhoods in Plant Populations

9708165卡斯珀这个项目的最终目标是测量植物根的横向扩展，并确定根面积如何随着特定的土壤条件和邻近植物的存在而变化。这里资助的为期一年的项目将主要测试最近设计的植物科学技术是否可以应用于这个问题。我们将测试铯、锂、钚和锶的同位素在多大程度上可以用作示踪剂，以确定植物是否从土壤空间的某个特定点吸收养分。这些元素起到了营养类似物的作用，这意味着植物应该吸收它们来代替普通的营养。因为它们在大多数土壤中很少见，我们可以将含有这些元素的溶液放置在土壤中的特定位置，并通过检测它们在新产生的植物组织中的存在，确保植物的根系与示踪剂的口袋相交。通过知道种群中有多少植物吸收了特定的示踪剂，我们可以准确地确定在示踪剂标记的区域有多少根系统重叠。在一个群体中使用所有四个示踪剂将使我们能够测量四个不同方向的根延伸，并有助于估计侧根面积。第二种技术将被应用于真菌-根联合(菌根)是否扩大了植物吸收养分的土壤面积的问题。戈尔-TEXR织物将用于从植物根中分离示踪剂。根部和营养物质不会穿过织物上的小孔，但菌根菌丝会。通过以这种方式将根与示踪剂物理隔离，我们可以确定菌根是否延长了植物吸收养分的距离。另一项实验将确定示踪剂是否在土壤中横向移动，即使在没有植物根的情况下。这些实验对于了解植物之间如何在地下竞争土壤资源是很重要的。我们可以测量地下竞争对植物生长的影响，但我们对哪些个体参与竞争知之甚少。我们不知道相互作用是否主要发生在最近的邻居之间，或者根系是否延伸到最近的邻居之外，包括许多其他植物。从挖掘的根系中确定这种信息是不可能的，因为在吸收养分方面最活跃的细根无法从土壤中恢复。这些信息对于确定相邻植物的数量和邻近程度如何影响植物生长至关重要，无论是在农业系统还是在自然系统中。

9708165 Casper The ultimate goals of this project are to measure the lateral spread of plant roots and to determine how rooting area changes with certain soil conditions and the presence of neighboring plants. The one year project funded here will primarily test whether recently devised techniques in plant science can be applied to this problem. We will test to what extent isotopes of cesium, lithium, rubidium, and strontium can be used as tracers to determine whether plants take up nutrients from a particular point in soil space. These elements serve as nutrient analogs which means that plants should take them up in place of common nutrients. Because they are rare within most soils, we can place solutions containing these elements at defined locations in the soil and by detecting their presence in newly produced plant tissue, be certain that the plant's root system intersects the pocket of tracer. By knowing how many of the plants in the population have taken up a particular tracer, we can determine exactly how many root systems overlap in the area marked by tracer. The use of all four tracers within a single population will enable us to measure root extension in four different directions and facilitate estimates of lateral rooting area. A second technique will be applied to the question of whether fungal-root associations mycorrhizae) enlarge the soil area over which a plant takes up nutrients. GORE-TEXR fabric will be used to separate tracer from plant roots. Roots and nutrients do not pass through the small pores in the fabric but mycorrhizal hyphae do. By physically isolating roots from tracers in this way, we can determine whether the mycorrhizae extend the distance over which a plant takes up nutrients. Another experiment will determine whether the tracer moves laterally in the soil even in the absence of plant roots. These experiments are important to understanding how below ground competition for soil resources takes place among plants. We can measure how the presenc e of below ground competition affects plant growth, but we have little knowledge of which individuals are engaged in the competition. We do not know whether interactions primarily occur between nearest neighbors or whether root systems extend beyond nearest neighbors to include many other plants. It is impossible to determine this information from excavating root systems because the fine roots that are most active in nutrient uptake cannot be recovered from the soil. This information is essential to determining how the number and proximity of neighboring plants affect plant growth, whether it be in agricultural or natural systems.