Data from: Increased root herbivory under elevated atmospheric carbon dioxide concentrations is reversed by silicon-based plant defences

Predicted increases in atmospheric concentrations of CO2 may alter the susceptibility of many plants to insect herbivores due to changes in plant nutrition and defences. Silicon plays a critical role in plant defence against herbivores, so increasing such silicon-based defences in plants may help remediate situations where plants become more susceptible to herbivores. Sugarcane (Saccharum spp. hybrid) were subjected to fully factorial treatment combinations of ambient (aCO2) or elevated (eCO2) atmospheric CO2 concentrations; ambient silicon or silicon supplementation; insect-free or subject to root herbivory by greyback canegrub (Dermolepida albohirtum). A glasshouse study was used to determine how these factors affected rates of photosynthesis, growth, chemistry (concentrations of silicon, carbon, nitrogen and non-structural carbohydrates). Changes in canegrub mass were determined in the glasshouse pot study, together with more detailed assessment of how eCO2 and silicon supplementation affected performance and feeding behaviour (relative growth rate and relative consumption) in a 24-hour feeding efficiency assay. eCO2 and silicon supplementation increased rates of photosynthesis (+32% and 14%, respectively) sugarcane biomass (+45% and 69%, respectively). Silicon supplementation increased silicon concentrations in both leaves and roots by 54% and 75%, respectively. eCO2 caused root C:N to increase by 12%. Canegrub performance and consumption increased under eCO2; relative growth rate (RGR) increased by 116% and consumed 57% more root material (suggestive of compensatory feeding). Silicon application reversed these effects, with large decreases in mass change, RGR and root consumption (65% less root mass consumed). Synthesis and applications. Our results suggest future atmospheric carbon dioxide concentrations could lead to increased crop damage by a below-ground herbivore. Increasing bioavailable silicon in soil stimulated silicon-based defences which dramatically decreased herbivory and herbivore performance. Our findings suggest future pest management strategies could benefit from characterising deficiencies in bioavailable silicon in agricultural soils and targeted application of silicon fertilisers. Moreover, future breeding programmes should exploit variation in silicon uptake between cultivars to enhance silicon uptake in new crop varieties. Silicon-based plant defence proved to be highly beneficial for remediating the negative effects of atmospheric change on sugarcane susceptibility to herbivory and could be applicable in other crops.大气二氧化碳（CO₂）浓度的预期升高，可能因植物营养与防御机制的变化，改变多数植物对昆虫植食者的易感程度。硅在植物对抗植食者的防御过程中发挥关键作用，因此强化植物的硅基防御（silicon-based defences）机制，或可改善植物对植食者易感程度升高的状况。 本研究以甘蔗（Saccharum spp.杂交种）为材料，设置完全因子组合处理：大气CO₂浓度分为环境水平（ambient CO₂, aCO₂）与升高水平（elevated CO₂, eCO₂）；硅处理分为环境硅浓度与硅补充（silicon supplementation）处理；虫害处理分为无虫组与受灰背蔗金龟（Dermolepida albohirtum）根部植食组。通过温室实验，探究上述因素对甘蔗光合速率、生长状况及化学组分（硅、碳、氮与非结构性碳水化合物（non-structural carbohydrates）浓度）的影响。在温室盆栽实验中测定灰背蔗金龟的体重变化，并通过24小时取食效率试验，更细致地评估eCO₂与硅补充处理对其取食表现与行为（相对生长率（Relative Growth Rate, RGR）与相对取食量（relative consumption））的影响。 eCO₂与硅补充处理分别提升了甘蔗的光合速率（分别提升32%与14%）与生物量（分别提升45%与69%）。硅补充处理分别使叶片与根系的硅浓度提升54%与75%；eCO₂处理使根系的碳氮比（C:N）升高12%。 eCO₂处理下，灰背蔗金龟的取食表现与取食量均有所提升：相对生长率（RGR）升高116%，取食的根系生物量增加57%（提示存在补偿性取食行为）。施加硅则逆转了上述效应，金龟的体重变化量、RGR与根系取食量均大幅下降（根系取食量减少65%）。 总结与应用。本研究结果表明，未来大气CO₂浓度的升高，可能会加重地下植食者对作物的为害程度。提升土壤中生物可利用硅（bioavailable silicon）的含量，可激活植物的硅基防御机制，从而显著降低植食为害与植食者的表现。本研究结果提示，未来的害虫管理策略可通过表征农田土壤的生物可利用硅缺乏状况，并针对性施用硅肥来优化。此外，未来的作物育种项目应利用不同品种间硅吸收能力的差异，提升新品种的硅吸收效率。硅基植物防御机制可有效改善大气变化引发的甘蔗对植食者易感程度升高的负面影响，且该策略可推广至其他作物。