Plants, Photosynthesis, and Soil, School of Biosciences, University of Sheffield, Sheffield, S10 2TN, UK.
Department of Biology, University of York, York, YO10 5DD, UK.
J Exp Bot. 2023 Sep 13;74(17):5363-5373. doi: 10.1093/jxb/erad224.
In response to herbivory, many grasses, including crops such as wheat, accumulate significant levels of silicon (Si) as an antiherbivore defence. Damage-induced increases in Si can be localized in damaged leaves or be more systemic, but the mechanisms leading to these differences in Si distribution remain untested. Ten genetically diverse wheat landraces (Triticum aestivum) were used to assess genotypic variation in Si induction in response to mechanical damage and how this was affected by exogenous Si supply. Total and soluble Si levels were measured in damaged and undamaged leaves as well as in the phloem to test how Si was allocated to different parts of the plant after damage. Localized, but not systemic, induction of Si defences occurred, and was more pronounced when plants had supplemental Si. Damaged plants had significant increases in Si concentration in their damaged leaves, while the Si concentration in undamaged leaves decreased, such that there was no difference in the average Si concentration of damaged and undamaged plants. The increased Si in damaged leaves was due to the redirection of soluble Si, present in the phloem, from undamaged to damaged plant parts, potentially a more cost-effective defence mechanism for plants than increased Si uptake.
为了应对食草动物的侵害，许多草类，包括小麦等作物，会积累大量的硅（Si）作为一种抗食草动物的防御机制。受损叶片中的 Si 含量增加可以是局部的，也可以是全身性的，但导致 Si 分布差异的机制仍未得到验证。本研究选用 10 种遗传多样性不同的小麦地方品种（Triticum aestivum），以评估对机械损伤的 Si 诱导的基因型变异，以及外源性 Si 供应如何影响这种变异。在受损和未受损叶片以及韧皮部中测量总 Si 和可溶 Si 水平，以测试 Si 在植物受损后是如何分配到不同部位的。研究发现，Si 防御系统发生了局部诱导，但不是全身性诱导，而当植物有外源 Si 时，这种诱导更为明显。受损植物的受损叶片中 Si 浓度显著增加，而未受损叶片中的 Si 浓度降低，因此受损和未受损叶片的平均 Si 浓度没有差异。受损叶片中增加的 Si 是由于韧皮部中存在的可溶 Si 从未受损部位向受损部位的重新分配，这可能是一种比增加 Si 吸收更具成本效益的植物防御机制。
