Jones Ian M, Koptur Suzanne
Department of Biological Sciences, Florida International University 11200 S.W. 8th Street, Miami, Florida 33199 USA.
Am J Bot. 2015 Jan;102(1):58-66. doi: 10.3732/ajb.1400381. Epub 2014 Dec 18.
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Extrafloral nectar (EFN) mediates food for protection mutualisms between plants and defensive insects. Understanding sources of variation in EFN production is important because such variations may affect the number and identity of visitors and the effectiveness of plant defense. We investigated the influence of plant developmental stage, time of day, leaf age, and leaf damage on EFN production in Senna mexicana var. chapmanii. The observed patterns of variation in EFN production were compared with those predicted by optimal defense theory.•
Greenhouse experiments with potted plants were conducted to determine how plant age, time of day, and leaf damage affected EFN production. A subsequent field study was conducted to determine how leaf damage, and the resulting increase in EFN production, affected ant visitation in S. chapmanii.•
More nectar was produced at night and by older plants. Leaf damage resulted in increased EFN production, and the magnitude of the response was greater in plants damaged in the morning than those damaged at night. Damage to young leaves elicited a stronger defensive response than damage to older leaves, in line with optimal defense theory. Damage to the leaves of S. chapmanii also resulted in significantly higher ant visitation in the field.•
Extrafloral nectar is an inducible defense in S. chapmanii. Developmental variations in its production support the growth differentiation balance hypothesis, while within-plant variations and damage responses support optimal defense theory.
研究前提：花外蜜（EFN）介导了植物与防御性昆虫之间的食物换保护互利共生关系。了解花外蜜分泌量变化的来源很重要，因为这种变化可能会影响访客的数量和种类以及植物防御的有效性。我们研究了植物发育阶段、一天中的时间、叶龄和叶片损伤对墨西哥决明变种查普曼决明花外蜜分泌的影响。将观察到的花外蜜分泌量变化模式与最佳防御理论预测的模式进行了比较。
方法：进行了盆栽植物温室实验，以确定植株年龄、一天中的时间和叶片损伤如何影响花外蜜的分泌。随后进行了田间研究，以确定叶片损伤以及由此导致的花外蜜分泌增加如何影响查普曼决明的蚂蚁访花情况。
主要结果：夜间和较老的植株分泌的花蜜更多。叶片损伤导致花外蜜分泌增加，早上受损植株的反应幅度大于夜间受损植株。幼叶受损引发的防御反应比老叶受损更强，这与最佳防御理论一致。查普曼决明叶片受损还导致田间蚂蚁访花显著增加。
结论：花外蜜是查普曼决明的一种诱导性防御。其分泌的发育变化支持生长分化平衡假说，而植株内的变化和损伤反应支持最佳防御理论。
