Valkama Elena, Koricheva Julia, Ossipov Vladimir, Ossipova Svetlana, Haukioja Erkki, Pihlaja Kalevi
Section of Ecology, Department of Biology, University of Turku, 20014 Turku, Finland.
Oecologia. 2005 Dec;146(3):385-93. doi: 10.1007/s00442-005-0216-z. Epub 2005 Oct 27.
Changes in morphology and chemistry of leaf surface in response to herbivore damage may increase plant resistance to subsequent herbivore attack; however, there is lack of studies on induced responses of glandular trichomes and their exudates in woody plants and on effects of these changes on herbivores. We studied delayed induced responses in leaf surface traits of five clones of silver birch (Betula pendula Roth) subjected to various types of mechanical defoliation and simulated winter browsing. Glandular trichome density and concentrations of the majority of surface lipophilic compounds increased in trees defoliated during the previous summer. This induced response was systemic, since control branches in branch defoliated trees responded to the treatments similarly to defoliated branches, but differently from control trees. In contrast to defoliation treatments, simulated winter browsing reduced glandular trichome density on the following summer and had fewer effects on individual surface lipophilic compounds. Moreover, constitutive density of glandular trichomes was negatively correlated with induced total amount of lipophilic compounds per trichome, indicating a trade-off between constitutive and induced resistance in silver birch. Induced changes in leaf surface traits had no significant effect on leaf damage by chewers, miners and gall mites, but increased susceptibility of birch trees to aphids. However, leaf damage by chewers, miners and gall mites in defoliated (but not in control) trees was correlated with concentrations of some fatty acids and triterpenoids, although the direction of relationships varied among herbivore species. This indicates that induction of surface lipophilic compounds may influence birch resistance to herbivores. Our study thus demonstrated both specificity of elicitation of induced responses of birch leaf surface traits by different types of damage and specificity of the effects of these responses on different types of herbivores.
叶片表面形态和化学性质因食草动物损害而发生的变化，可能会增强植物对后续食草动物攻击的抗性；然而，关于木本植物中腺毛及其分泌物的诱导反应，以及这些变化对食草动物的影响，目前缺乏相关研究。我们研究了五个银桦（Betula pendula Roth）无性系在遭受不同类型的机械去叶和模拟冬季啃食后，叶片表面性状的延迟诱导反应。前一年夏季去叶的树木中，腺毛密度以及大多数表面亲脂性化合物的浓度增加。这种诱导反应具有系统性，因为去叶树枝上的对照枝条对处理的反应与去叶枝条相似，但与对照树不同。与去叶处理相反，模拟冬季啃食在次年夏季降低了腺毛密度，对单个表面亲脂性化合物的影响较小。此外，腺毛的组成密度与每个腺毛诱导产生的亲脂性化合物总量呈负相关，这表明银桦在组成抗性和诱导抗性之间存在权衡。叶片表面性状的诱导变化对咀嚼式口器昆虫、潜叶虫和瘿螨造成的叶片损害没有显著影响，但增加了桦树对蚜虫的易感性。然而，去叶（而非对照）树木中咀嚼式口器昆虫、潜叶虫和瘿螨造成的叶片损害与某些脂肪酸和三萜类化合物的浓度相关，尽管不同食草动物物种之间关系的方向有所不同。这表明表面亲脂性化合物的诱导可能会影响桦树对食草动物的抗性。因此，我们的研究既证明了不同类型损害引发桦树叶片表面性状诱导反应的特异性，也证明了这些反应对不同类型食草动物影响的特异性。
