Laboratoire Evolution et Diversité Biologique, UMR 5174 CNRS/Université Paul Sabatier, 118 route de Narbonne, Toulouse, France.
Phytochemistry. 2012 Oct;82:81-8. doi: 10.1016/j.phytochem.2012.07.003. Epub 2012 Aug 2.
Volatile terpenes are among the most diverse class of defensive compounds in plants, and they are implicated in both direct and indirect defense against herbivores. In terpenes, both the quantity and the diversity of compounds appear to increase the efficiency of defense as a diverse blend of compounds provides a more efficient protection against a broader range of herbivores and limits the chances that an enemy evolves resistance. Theory predicts that plant defensive compounds should be allocated differentially among tissues according to the value of the tissue, its cost of construction and the herbivore pressure on it. We collected volatile terpenes from bark and leaves of 178 individual tree belonging to 55 angiosperm species in French Guiana and compare the kind, amount, and diversity of compounds in these tissues. We hypothesized that in woody plants, the outermost part of the trunk should hold a more diverse blend of volatile terpenes. Additionally, as herbivore communities associated with the leaves is different to the one associated with the bark, we also hypothesized that terpene blends should be distinct in the bark vs. the leaves of a given species. We found that the mixture of volatile terpenes released by bark is different and more diverse than that released by leaves, both in monoterpenes and sesquiterpenes. This supports our hypothesis and further suggests that the emission of terpenes by the bark should be more important for trunk defense than previously thought.
挥发性萜类化合物是植物中防御化合物最多样化的一类，它们与植物对草食动物的直接和间接防御都有关联。在萜类化合物中，化合物的数量和多样性似乎都提高了防御的效率，因为多种化合物的混合可以更有效地保护植物免受更广泛范围的草食动物侵害，并限制了敌人进化出抗性的机会。理论预测，植物防御化合物应该根据组织的价值、构建成本以及草食动物对其的压力，在不同的组织中进行差异化分配。我们从法属圭亚那的 178 株不同的被子植物个体的树皮和叶片中收集了挥发性萜类化合物，并比较了这些组织中化合物的种类、数量和多样性。我们假设，在木本植物中，树干的最外层应该含有更多样化的挥发性萜类化合物混合物。此外，由于与叶片相关的草食动物群落与与树皮相关的草食动物群落不同，我们还假设萜类化合物混合物在同一物种的树皮和叶片之间应该是不同的。我们发现，树皮释放的挥发性萜类混合物无论是在单萜烯还是倍半萜烯方面，都与叶片释放的混合物不同且更具多样性。这支持了我们的假设，并进一步表明，与之前的想法相比，树皮萜类化合物的排放对树干防御更为重要。
