Expansion Rates and Defenses in Young Leaves of Tropical Species

植物进化出一系列物理和化学防御 保护他们免受放牧伤害（食草动物）。 大部分 我们对食草动物和植物防御的理解来自于 研究成熟的叶子。 然而，年轻的扩展叶 叶子生命中最脆弱的阶段 八十 百分之一百的终身损坏发生在这个短暂的窗口期间， 因为扩展的叶子遭受10-100倍的伤害 从真菌和食草动物那里获取的成熟的叶子。 我们有兴趣 了解幼叶防御的有效性， 防御之间的互动。 特别是，我们假设， 叶片迅速展开，减少了脆弱期， 与其他防御如韧性、化学 防御和绿化。 虽然化学防御和快速 膨胀是幼叶的两种最有效的防御， 在叶片扩展过程中合成的化学物质可能会导致自动 毒性以及竞争资源用于快速叶 建设 具有缓慢扩展的嫩叶的物种 因此，可能更广泛地依赖于有效的化学品 防御 我们将描述化学防御的特点， 雨林植物中快速和缓慢扩张的嫩叶， 量化这些化学物质作为防御的有效性， 食草昆虫和真菌病原体。 除了让我们深入了解这个生态系统， 重要的相互作用，研究将提供新的数据 和有效的化合物。 出于方便，大多数 筛选生物活性化合物已经使用成熟的 叶，即使这个年龄段主要是捍卫 韧性和单宁。 因为嫩叶很嫩， 主要是防御性化学品，以保护它们免受食草动物的伤害。 我们预测，在嫩叶中发现的化学物质类型 移动的，在小浓度和小浓度下有效， 分子量，所有的属性，使他们更 适合医药和农业发展。

Plants have evolved a battery of physical and chemical defenses which protect them against grazing damage (herbivory). Most of our understanding of herbivory and plant defenses derives from research on mature leaves. However, young expanding leaves are the most vulnerable stage during the life of a leaf. Eighty percent of the lifetime damage occurs during this short window, because expanding leaves suffer 10-100 times the rates of damage from fungi and herbivores as mature leaves. We are interested in understanding the effectiveness of young leaf defenses, and the interactions among defenses. In particular, we hypothesize that rapid leaf expansion, which reduces the vulnerable period, is incompatible with other defenses such as toughness, chemical defenses and greening. Although chemical defense and rapid expansion are the two most effective defenses for young leaves, synthesis of chemicals during leaf expansion may cause auto- toxicity as well as compete for resources used in rapid leaf construction. Species which have slowly expanding young leaves may therefore rely more extensively on effective chemical defense. We will characterize the chemical defense profiles of fast- and slow-expanding young leaves in rainforest plants, and quantify the effectiveness of these chemicals as defenses against insect herbivores and fungal pathogens. In addition to giving us insight into the ecology of this important interaction, the research will provide data on novel and effective chemical compounds. Out of convenience, most screening for biologically active compounds has used mature leaves, even though this age-class is primarily defended by toughness and tannins. Since young leaves are tender, they rely primarily on defensive chemicals to protect them from herbivores. We predict that the types of chemicals found in young leaves will be mobile, effective in small concentrations and of small molecular weight, all attributes that make them much more tractable for medicinal and agricultural development.