CAA: Analyses of Chemical Defenses in Young Leaves of Tropical Species

小行星9407835 在热带雨林中，食草动物对植物的捕食大多发生在嫩叶上。 受害率比成熟叶片高20倍，70%的终生损害发生在叶片扩展的短期内。 伤害很高，因为嫩叶很嫩，富含蛋白质。 韧性，最有效的防御，是不可能在叶片扩展。 这表明其他防御，包括次生化学代谢物，可能在幼叶中特别重要。 对化合物的螯合、回收和周转率的理论考虑也表明，嫩叶应该含有多种化学防御。 然而，以前的研究，量化总酚或单宁浓度无法解释物种之间的变化率草食动物。 因此，为了充分了解热带植物-食草动物的相互作用，需要对幼叶的化学防御进行更详细的研究。 PI建议通过分离和鉴定尽可能多的化合物来检查幼叶中的次级代谢产物。 分离化合物的威慑或毒性活性将使用一套天敌进行测试，范围从病毒，细菌和真菌到昆虫。 这些复杂的化学分析将使PI能够解决有关植物-食草动物相互作用的各种生态和进化问题，包括：1）当前理论在预测嫩叶中次生代谢物的多样性方面是否正确？ 2)为什么一个物种会有多种次生代谢产物？ 它是一种适应性反应的多样性天敌的发生？ 3)有人认为，次生代谢产物的合成可能与幼叶的另一种主要防御生理学上不相容，即快速扩展以缩短脆弱期。 这项研究中收集的数据将有助于阐明所有这些有趣的生态问题。

9407835 Coley In tropical rainforest, most predation on plants by herbivores occurs on young leaves. Rates of damage are 20 times higher than on mature leaves, and 70% of the lifetime damage takes place during the short period of leaf expansion. Damage is high because young leaves are tender and rich in protein. Toughness, the most effective defense, is not possible during leaf expansion. This suggests that other defenses, including secondary chemical metabolites, may be particularly important in young leaves. Theoretical considerations of sequestration, reclamation and turnover rates of compounds also suggest that young leaves should contain a diversity of chemical defenses. However, previous studies that quantified total phenolic or tannin concentrations were unable to explain variation among species in rates of herbivory. Thus a more detailed perspective of chemical defense in young leaves is needed in order fully to understand plant-herbivore interactions in the tropics. The PI proposes to examine the secondary metabolites in young leaves by isolating and identifying as many compounds as possible from each of a few species. The deterrent or toxic activity of isolated compounds will be tested using a suite of natural enemies ranging from viruses, bacteria and fungi to insects. These sophisticated chemical analyses will allow the PI to address a variety of ecological and evolutionary questions about plant-herbivore interactions, including: 1) are current theories correct in predicting a great diversity of secondary metabolites in young leaves? 2) Why does a single species have a variety of secondary metabolites? Is it an adaptive response to the occurrence of a diversity of natural enemies? 3) It has been argued that synthesis of secondary metabolites may be physiologically incompatible with another major defense of young leaves, namely rapid expansion to shorten the period of vulnerability. The data gathered in this study will shed much light on all these intriguing ecologi cal problems.