Hawkesbury Institute for the Environment, Western Sydney University, Penrith, NSW, Australia.
College of Agriculture and Veterinary Medicine, Jimma University, Jimma, Ethiopia.
Glob Chang Biol. 2021 Jun;27(12):2959-2969. doi: 10.1111/gcb.15619. Epub 2021 Apr 14.
Silicon (Si) has an important role in mitigating diverse biotic and abiotic stresses in plants, mainly via the silicification of plant tissues. Environmental changes such as atmospheric CO concentrations may affect grass Si concentrations which, in turn, can alter herbivore performance. We recently demonstrated that pre-industrial atmospheric CO increased Si accumulation in Brachypodium distachyon grass, yet the patterns of Si deposition in leaves and whether this affects insect herbivore performance remains unknown. Moreover, it is unclear whether CO -driven changes in Si accumulation are linked to changes in gas exchange (e.g. transpiration rates). We therefore investigated how pre-industrial (reduced; rCO , 200 ppm), ambient (aCO , 410 ppm) and elevated (eCO , 640 ppm) CO concentrations, in combination with Si-treatment (Si+ or Si-), affected Si accumulation in B. distachyon and its subsequent effect on the performance of the global insect pest, Helicoverpa armigera. rCO increased Si concentrations by 29% and 36% compared to aCO and eCO respectively. These changes were not related to observed changes in gas exchange under different CO regimes, however. The increased Si accumulation under rCO decreased herbivore relative growth rate (RGR) by 120% relative to eCO whereas rCO caused herbivore RGR to decrease by 26% compared to eCO . Si supplementation also increased the density of macrohairs, silica and prickle cells, which was associated with reduced herbivore performance. There was a negative correlation among macrohair density, silica cell density, prickle cell density and herbivore RGR under rCO suggesting that these changes in leaf surface morphology were linked to reduced performance under this CO regime. To our knowledge, this is the first study to demonstrate that increased Si accumulation under pre-industrial CO reduces insect herbivore performance. Contrastingly, we found reduced Si accumulation under higher CO , which suggests that some grasses may become more susceptible to insect herbivores under projected climate change scenarios.
硅（Si）在减轻植物的多种生物和非生物胁迫方面起着重要作用，主要通过植物组织的硅化作用。环境变化，如大气 CO 浓度，可能会影响草的硅浓度，进而改变食草动物的表现。我们最近证明，前工业化时期的大气 CO 增加了短柄草的硅积累，但叶片中硅的沉积模式以及这是否会影响昆虫食草动物的表现仍不清楚。此外，尚不清楚 CO 驱动的硅积累变化是否与气体交换（例如蒸腾速率）的变化有关。因此，我们研究了前工业化（减少；rCO，200ppm）、环境（aCO，410ppm）和升高（eCO，640ppm）CO 浓度与 Si 处理（Si+或 Si-）相结合如何影响短柄草的硅积累及其对全球害虫烟粉虱表现的后续影响。与 aCO 和 eCO 相比，rCO 分别使 Si 浓度增加了 29%和 36%。然而，这些变化与不同 CO 条件下观察到的气体交换变化无关。与 eCO 相比，rCO 下增加的硅积累使食草动物的相对生长率（RGR）降低了 120%，而 rCO 使食草动物的 RGR 比 eCO 降低了 26%。Si 补充还增加了宏观毛、硅和刺细胞的密度，这与食草动物表现降低有关。在 rCO 下，宏观毛密度、硅细胞密度、刺细胞密度与食草动物 RGR 之间存在负相关，这表明叶片表面形态的这些变化与该 CO 条件下的性能降低有关。据我们所知，这是第一项证明前工业化 CO 下增加的硅积累会降低昆虫食草动物表现的研究。相比之下，我们发现在更高的 CO 下硅积累减少，这表明在预测的气候变化情景下，一些草可能更容易受到昆虫食草动物的侵害。
