Department of Ecology and Evolutionary Biology, UCB 334, University of Colorado, Boulder, Colorado 80309, USA.
Am J Bot. 2012 Oct;99(10):1630-7. doi: 10.3732/ajb.1100492. Epub 2012 Sep 4.
Human nitrogen (N) inputs to terrestrial ecosystems have greatly increased in recent years and may have important consequences for plant growth, reproduction, and defense. Although numerous studies have investigated the effects of nitrogen addition on plants, few have examined both above- and belowground responses within a range of predicted increase and apart from concomitant increases in other nutrients. •
We conducted a greenhouse experiment to study the consequences of increased nitrogen inputs, such as those from atmospheric N deposition, on plant performance, chemical defenses, and allocation tradeoffs for an invasive species, Linaria dalmatica. This plant produces iridoid glycosides, which are a group of terpenoid compounds. •
Soil nitrogen enrichment increased growth, reproduction, and whole-plant iridoid glycosides while decreasing some costs of defense. Interestingly, nitrogen addition had varying effects on defense allocation to above- and belowground tissues. Specifically, there was no change in iridoid glycoside concentrations of shoots, whereas concentrations decreased in flowers by ~35% and increased in roots by >400%. •
Observed increases in plant performance and chemical defenses may have implications for the invasion potential of L. dalmatica. Moreover, our results highlight the importance of evaluating both above- and belowground plant defenses. In particular, findings presented here indicate that research focused on leaf-level defenses may not detect key allelochemical responses, including changes in plant resistance traits that could affect consumers (e.g., herbivores and pathogens) that specialize on different plant tissues as well as plant fitness and invasion success.
近年来，人类向陆地生态系统输入的氮（N）大大增加，这可能对植物的生长、繁殖和防御产生重要影响。尽管许多研究已经调查了氮添加对植物的影响，但很少有研究在预测的增加范围内，除了其他养分的伴随增加之外，同时研究地上和地下的反应。
我们进行了一项温室实验，研究了氮输入的增加（如大气氮沉积）对入侵物种林达利亚达玛蒂卡（Linaria dalmatica）的植物性能、化学防御和分配权衡的影响。这种植物产生了裂环烯醚萜糖苷，这是一组萜烯化合物。
土壤氮素富集增加了生长、繁殖和全株裂环烯醚萜糖苷含量，同时降低了一些防御成本。有趣的是，氮添加对地上和地下组织的防御分配有不同的影响。具体来说，茎中的裂环烯醚萜糖苷浓度没有变化，而花中的浓度下降了约 35%，根中的浓度增加了超过 400%。
观察到的植物性能和化学防御的增加可能对林达利亚达玛蒂卡的入侵潜力产生影响。此外，我们的结果强调了评估地上和地下植物防御的重要性。特别是，这里提出的研究结果表明，专注于叶片防御的研究可能无法检测到关键的化感反应，包括植物抗性特征的变化，这些变化可能会影响专门针对不同植物组织的消费者（如食草动物和病原体）以及植物的适应性和入侵成功。
