EAGER: Collaborative Proposal: Linking physiology and morphology in Grassland evolution via a novel analytical technique

草地覆盖地球陆地表面的40%，在陆地生命，全球气候和关键的人力资源中发挥着关键作用（禾本科包括所有谷类作物，如水稻和小麦）。虽然它们出现在约7000万年前，但草原的扩张仅在约2200万年前开始，热带稀树草原生态系统在约800万年前就存在了。草的进化和生态系统的变化可能与气候、景观和动物的演变相吻合。鉴定草化石的最好方法是从显微镜下的硅质碎片（“植硅石”）中，当植物的其余部分分解时，它们会留在沉积岩中。植硅石具有特定草类型的形状特征，但没有方法可以揭示产生它们的草的光合作用类型（C3或C4）。该项目测试了一种新的方法，使用植硅石来测量它们内部未分解碳的化学成分;因此，产生它们的草的光合作用类型。这将使研究人员能够回答有关草原的过去和可能的未来的问题。例如，什么草生长在最早的热带稀树草原上，它们利用什么光合作用？是什么导致了C4草的传播？随着地球大气和气候的持续变化，会发生什么？ 这个跨学科的项目将利用精确的样品制备和原位分析方法来表征1。植硅体中弥散碳和吸留碳的分布; 2.这些水库的碳同位素比值，反映光合作用途径。该项目将首先比较温室种植标本的叶子和植硅体化学，然后转移到土壤中，最终目标是应用于化石系统。所提出的方法，一旦完全开发，可以在世界各地的许多实验室执行，并将代表分析植物学的一个重大飞跃。这项工作将应用于广泛的主题，包括草原和原始人类进化之间的关系。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

Grasslands cover ~40% of Earth’s land surface, playing a key role in terrestrial life, global climate and critical human resources (the grass family includes all cereal crops like rice and wheat). Although they appeared ~70 million years ago, the spread of grasslands began only ~22 million years ago, with tropical savanna ecosystems present by ~8 million years ago. Grass evolution and ecosystem change likely coincided with evolving climates, landscapes and animals. The best way to identify fossil grasses is from microscopic silica pieces (“phytoliths”), left behind in sedimentary rocks when the rest of the plant has decomposed. Phytoliths have shapes characteristic of particular grass types, but no method exists that can reveal the photosynthesis type (C3 or C4) of the grass that produced them. This project tests a new method to use phytoliths to measure the chemistry of un-decomposed carbon inside them; thus, the photosynthetic type of the grasses that produced them. This will allow researchers to answer questions about the past and possible future of grasslands. For example, what grasses grew in the earliest savannas and what photosynthesis did they use? What caused the spread of the C4 grasses, and what will happen as Earth’s atmosphere and climate continue to change? This cross-disciplinary project will utilize precision sample preparation and in-situ analytical methods to characterize 1. the distribution of disseminated and occluded carbon in phytoliths, and 2. the carbon isotopic ratios of these reservoirs, reflecting photosynthetic pathway. The project will first compare leaf and phytolith chemistry of greenhouse-grown specimens and move on to soils with the ultimate goal of application to fossil systems. The proposed method, once fully developed, can be executed at many laboratories world-wide and will represent a major leap forward in analytical phytology. This work will have applications to a wide range of topics including the relationships between grassland and hominid evolution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.