Entomology and Nematology Department, University of Florida, Gainesville, Florida, USA.
Laboratório de Ecologia Comportamental e de Interações (LECI), Instituto de Biologia. Universidade Federal de Uberlândia, Uberlândia, Brazil.
Ecology. 2023 May;104(5):e4029. doi: 10.1002/ecy.4029. Epub 2023 Mar 28.
Plants have evolved inducible defenses that allow them to minimize costs associated with the production of constitutive defenses when herbivores are not present. However, as a consequence, some plants might experience a period of vulnerability between damage and the onset of defense and/or between the cessation of damage and relaxation of defense. Few studies have examined the time course in the inducible protective mutualism between ants and extrafloral nectary (EFN)-bearing plants. None has compared the inducibility of EFNs on vegetative versus reproductive parts or in response to different levels of herbivore damage. Here, we disentangle the inducibility process by evaluating extrafloral nectar production and ant attendance over time, the time course of inducibility on different plant parts, and the time course of inducibility in response to different levels of foliar damage in a Brazilian tree, Qualea multiflora (Vochysiaceae). Using simulated herbivory on leaves and flowers, we found that (a) the production of extrafloral nectar from foliar and floral EFNs, as well as ant attendance, exhibited a lag between the moment of damage and the peak of response, followed by a response peak (usually 24 h after damage) at which the defense remains at its maximum level, then declines to prestimulus levels; (b) the time course of inducibility and the peak activity did not differ between EFNs located in vegetative versus reproductive parts, except for sugar concentration, which was higher in EFNs on vegetative parts; and (c) the time course of inducibility of foliar EFNs depended on damage level. Although considered a cost-saving strategy, inducible defenses can be disadvantageous since they can leave plants vulnerable to attack for extended periods. Our results illuminate the dynamics of the induced response and the underlying mechanisms that might mediate it, ultimately providing new insights into defense strategies employed by plants.
植物已经进化出诱导防御机制，使它们在没有食草动物时，能够将与组成性防御相关的成本最小化。然而，作为结果，一些植物可能会在遭受损害和防御开始之间以及在损害停止和防御放松之间经历一段脆弱期。很少有研究检查蚂蚁和具有额外花蜜腺（EFN）的植物之间诱导性保护共生的时间进程。没有研究比较过 EFN 在营养体和生殖体上的诱导能力，或者对不同程度的食草动物损害的反应。在这里，我们通过评估随时间推移的额外花蜜产生和蚂蚁出勤、不同植物部位的诱导能力时间进程以及对不同程度叶部损害的反应时间进程来解开诱导过程。在巴西的一种树木 Qualea multiflora（金虎尾科）中，我们使用模拟的叶片和花朵损害，发现（a）来自叶部和花部 EFN 的额外花蜜的产生，以及蚂蚁出勤，在损害时刻和反应高峰之间存在滞后，然后是反应高峰（通常在损害后 24 小时），此时防御处于最大水平，然后下降到刺激前水平；（b）诱导能力的时间进程和高峰活动在营养体和生殖体上的 EFN 之间没有差异，除了糖浓度，营养体上的 EFN 较高；（c）叶部 EFN 的诱导能力时间进程取决于损害水平。虽然被认为是一种节省成本的策略，但诱导防御可能会带来劣势，因为它们会使植物在较长时间内容易受到攻击。我们的结果阐明了诱导反应的动态及其潜在机制，最终为植物采用的防御策略提供了新的见解。
