HOW TO BE SWEET? EXTRAFLORAL NECTAR ALLOCATION BY GOSSYPIUM HIRSUTUM FITS OPTIMAL DEFENSE THEORY PREDICTIONS
HOW TO BE SWEET? EXTRAFLORAL NECTAR ALLOCATION BY GOSSYPIUM HIRSUTUM FITS OPTIMAL DEFENSE THEORY PREDICTIONS
复制标题
如何变得甜蜜？
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
Claire Bonifay
中科院分区：
文献类型：
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作者：
F. Wäckers;Claire Bonifay
植物利用花蜜有两种不同的功能。花蜜历来被视为授粉的范畴。另一方面，花外花蜜可以起到间接防御的作用，允许植物招募捕食者和寄生蜂。虽然这有助于明确分类，但在现实中，这些职能可能不会如此离散。花外花蜜可能在授粉中起作用，而花蜜可以被捕食者和寄生蜂利用，从而有助于植物防御。在这里，我们使用最优防御理论来生成关于防御性花蜜分配模式的预测。然后，使用棉花的苞片和叶部花蜜的生产模式的新数据来验证这些预测。苞片花蜜产量在开花当天有一个明显的高峰，随后在果实成熟时分泌较长时间。这表明花托蜜腺在授粉和防御中起着重要作用。花被蜜腺的构成花蜜产量比叶蜜腺分泌的花蜜多80到110倍。当食草动物对叶片造成伤害后，叶片蜜腺的花蜜产生是诱导的，而花被蜜腺的花蜜产生不是对果实伤害的反应，当果实结构受到草食的影响时，花蜜的产生甚至减少。这表明，间接防御的可诱导变体和构成变体都可以出现在一个植物物种中。这种花蜜分配模式符合最优防御理论，该理论预测，在水果等有价值的组织中存在高水平的结构性防御，而在叶片等价值较低的组织中存在诱导防御。这一结果支持了间接防御在花托蜜腺进化中是一种选择性力量的解释。虽然最优防御理论仅根据攻击概率和植物结构的价值来描述直接防御分配，但我们认为食草动物的可及性是影响间接防御分配的另一个因素。
Plants employ nectar for two distinct functions. Floral nectar has traditionally been viewed in the context of pollination. Extrafloral nectar on the other hand, can act as an indirect defense, allowing the plant to recruit predators and parasitoids. Whereas this makes for a clear-cut categorization, in reality the functions may not be so discrete. Extrafloral nectar may serve a role in pollination, while floral nectar can be utilized by predators and parasitoids and thus can contribute to plant defense. Here we use the optimal defense theory to generate predictions with respect to allocation patterns of defensive nectar. These predictions are then tested using novel data on the production patterns of bracteal and foliar nectar in cotton, Gossypium hirsutum. Bracteal nectar production shows a distinct peak on the day of anthesis, followed by a prolonged secretion during fruit maturation. This suggests that bracteal nectaries function in pollination as well as defense. Constitutive nectar production at the bracteal nectaries exceeds foliar nectar secretion by a factor of between 80 and 110. Whereas nectar production at foliar nectaries is induced following herbivore damage to leaves, bracteal nectar production is not induced in response to fruit damage and even decreases when the fruiting structure is subjected to herbivory. This shows that both an inducible and a constitutive variant of an indirect defense can occur within one plant species. This pattern of nectar allocation fits the optimal defense theory, which predicts high levels of constitutive defenses in valuable tissues such as fruits and induced defenses in less valuable tissues such as leaves. This result lends support to the interpretation that indirect defense has been a selective force in the evolution of bracteal nectaries. Although optimal defense theory has described direct defense allocation solely in terms of probability of attack and value of the plant structure, we argue that herbivore accessibility is an additional factor shaping the allocation of indirect defenses.