Department of Biological Sciences, CW-405 Biological Sciences Building, University of Alberta, Edmonton, AB, T6G 2E9, Canada.
Am J Bot. 2018 Sep;105(9):1491-1498. doi: 10.1002/ajb2.1154. Epub 2018 Sep 10.
The rapid leaf movement of Mimosa pudica is expected to be costly because of energetic trade-offs with other processes such as growth and reproduction. Here, we assess the photosynthetic opportunity cost and energetic cost of the unique leaf closing behavior of M. pudica.
In the greenhouse, we employed novel touch-stimulation machines to expose plants to one of three treatments: (1) untouched control plants; (2) plants touch-stimulated to close their leaves during the day to incur energetic costs associated with leaf movement and reduced photosynthesis; (3) plants touched at night to assess the effects of touch alone. M. pudica is nyctinastic and closes its leaves at night; thus, touching at night does not impart additional costs. We directly assessed costs by comparing physical traits. Leaf re-opening response was measured to assess the potential for plant behavioral plasticity to impact photosynthetic opportunity costs.
The cost of rapid leaf closure behavior was expressed as a 47% reduction in reproductive biomass accounting for the effect of touch. Touch itself changed physical traits such as biomass, with touched plants being generally bigger. Plants touched at night re-opened their leaflets 26% quicker than plants touched during the day.
We reason that the reproductive allocation costs incurred by M. pudica can be attributed to a combination of photosynthetic opportunity cost and the energetic cost associated with increased stimulation of leaf movement and that behavioral plasticity has the potential to alter photosynthetic opportunity costs.
含羞草的叶子快速运动预计会带来成本，因为这与生长和繁殖等其他过程存在能量权衡。在这里，我们评估了含羞草独特的叶子闭合行为的光合作用机会成本和能量成本。
在温室中，我们使用新型触摸刺激机将植物暴露于三种处理之一：（1）未受触摸的对照植物；（2）白天触摸刺激植物使其叶子闭合，以产生与叶子运动和光合作用减少相关的能量成本；（3）夜间触摸植物，以评估触摸本身的影响。含羞草是昼行性的，晚上会闭合叶子；因此，夜间触摸不会带来额外的成本。我们通过比较物理特征直接评估成本。测量叶子重新张开的反应，以评估植物行为可塑性对光合作用机会成本的潜在影响。
快速叶子闭合行为的成本表现为生殖生物量减少 47%，这是触摸的影响。触摸本身改变了生物量等物理特征，触摸过的植物通常更大。夜间触摸的植物比白天触摸的植物更快地重新打开小叶 26%。
我们推断，含羞草的生殖分配成本可归因于光合作用机会成本和与增加叶子运动刺激相关的能量成本的组合，并且行为可塑性有可能改变光合作用机会成本。
