DISSERTATION RESEARCH: Does Herbivory Signal Plants to Increase Nitrogen Uptake and Bolster Nitrogen and Starch Storage?

当植物受到咀嚼叶子的食草动物的攻击时，它们必须应对叶子组织的损失，叶子组织保存着植物丰富的营养物质，对从阳光中获取能量以促进生长很重要。植物可以将一些能量和营养储存在坚硬的组织中，比如茎和根，这是许多食草动物不容易吃的。淀粉和蛋白质是植物中最常见的储存化合物。在最近的研究中，放射性碳的使用使得研究活植物的分配过程成为可能。一项这样的研究表明，植物可能会增加对草食的储存。茉莉酸（jasmonic acid， JA）是一种重要的信号分子，参与植物对食草动物攻击的识别，增加了放射性碳向杨树和白杨幼树下部茎和根的运输量。本文提出的研究将确定JA和虫食是否会导致杨树和白杨茎和根中储存化合物的增加以及根对营养物质的摄入增加。将利用对植物重要的元素（碳-11、氮-13）的放射性同位素在活的植物中研究短期过程。储存化合物的长期积累将通过稳定同位素（碳-13、氮-15）和化学分析进行检验。在食草动物开始咀嚼叶子后，氮的吸收增加，碳和氮储存化合物的积累增加，这表明植物可以调节它们的代谢，以最大限度地提高它们在叶子损失和损害中生存的能力，并提高它们的再生能力。这项针对食草动物信号的储存调节的开创性研究对于理解植物如何进化以应对食草动物是必要的。此外，对植物如何耐受损害的更好理解可能会影响商业农业和林业做法，并可能产生操纵植物以改善生存和生长的见解。

When plants are attacked by leaf-chewing herbivores, they must cope with the loss of leaf tissues, which hold an abundance of the plant's nutrients and are important for capturing energy from sunlight for growth. Plants can store some of their energy and nutrients in tougher tissues, such as stems and roots that many herbivores cannot eat as readily. Starch and proteins are the most common storage compounds in plants. The use of radioactive carbon in recent research has allowed the study of allocation processes in living plants. One such study indicates that plants might increase storage in response to herbivory. An important signal molecule, jasmonic acid (JA), involved in plant recognition of herbivore attack increased the amount of radioactive carbon transported to the lower stem and roots in poplar and aspen tree saplings. The research proposed here will determine whether JA and insect herbivory cause increases in storage compounds in the stem and roots and increased nutrient intake by the roots of poplars and aspens. Short-term processes will be studied in living plants using radioactive isotopes of elements important to plants (carbon-11, nitrogen-13). The longer-term build-up of storage compounds will be examined using stable isotopes (carbon-13, nitrogen-15) and chemical analysis. Increased nitrogen uptake and increased build-up of carbon and nitrogen storage compounds following the initiation of herbivore leaf-chewing would indicate that plants can adjust their metabolism to maximize their ability to survive leaf loss and damage and to improve their re-growth. This pioneering research of storage regulation in response to herbivore signals will be necessary to understand how plants have evolved to cope with herbivory. Moreover, an improved understanding of how plants tolerate damage may influence commercial agricultural and forestry practices, and could generate insights for manipulating plants to improve survival and growth.