Dissertation Research: A Field-Test of Damage-induced Alkaloidal Defenses in Wild Tobacco

食草动物在植物中诱导的防御机制已经有了很好的文献记载，但缺乏这些诱导变化保护植物的田间证据。将研究危害引起的野生烟草叶片生物碱含量的增加。目前，关于这种诱导防御系统工作原理的机械信息已经足够多，可以提出对其生态意义进行实地测试。通过先前测试的实验设计，包括人为破坏生长在得克萨斯州南部的两组野生爬行动物植物，荷尔蒙抑制其中一组的生物碱反应，测量诱导和抑制植物及其各自的生物碱成分所承受的天然食草量，以下三个问题将被解决：1)这些伤害诱导的生物碱水平是否起到了反食草动物防御的作用？2)这种诱导防御在生殖产量方面是否代价高昂？3)不同野生烟草种群之间的食草性是否存在差异，这种差异是否与这种诱导防御的效益(减少食草性)和成本(繁殖成本)的差异相关？该项目是为数不多的同时测量叶片化学成分和食草动物表现的诱导植物抗性的田间研究之一。此外，这是第一次通过抑制受损植物的防御来研究诱导防御的有效性，也是第一个衡量防御的繁殖成本的项目。

Herbivore-induced defense in plants is well documented, but field evidence that these induced changes protect plants is lacking. The damage-induced increases in leaf alkaloid content in wild tobacco will be studied. Currently enough mechanistic information on the workings of this induced defense system to propose a field test of its ecological significance is available. With a previously tested experimental design that involves artificially damaging two groups of wild Nicotiana repanda plants growing in south-Texas, hormonally supressing the alkaloidal respose in one group, measuring the amount of natural herbivory sustained by induced and suppressed plants and their respective alkaloid coantents, the following three questions will be addressed: 1) are these damage-induced alkaloid levels functioning as an antiherbivore defense? 2) is this induced- defense costly in terms of reproductive output? and 3) is there variation in herbivory between different populations of wild tobacco, and is this variation correlated with variation in the benefit (reduced herbivory) and cost (reproductive costs) of this induced defense? This project is one of the few field studies of induced plant resistance which simultaneously measures both leaf chemistry and herbivore performance. Moreover, it is the first time the efficacy of an induced defense has been studied by inhibiting the defense in damaged plants, and the first project to measure the reproductive cost of defense.