Effect of silicon application on rice plant defence against brown planthopper feeding under climate change conditions

Silicon (Si) is known to enhance plant resistance in rice and other Poaceae plants by priming chemical defence, physiological, and mechanical barriers. However, the effects of application of Si to the soil on plant defence through antioxidative enzymes and changes in the nutrient composition of soil and rice straw under climate change conditions remain unclear. Thus this study was aimed at investigating the effects of Si on plant defence and other biochemical changes in the brown planthopper (BPH), Nilaparvata lugens (Stål, 1854), soil and rice plants under elevated CO₂ levels (570 ± 25 ppm) and elevated temperature (≃3°C higher than ambient) in open-top chambers (OTCs) during the rainy season of 2019 and 2020. The results revealed that under elevated CO₂, Si amendment significantly enhanced the activity of defensive antioxidative enzymes, namely catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) upon BPH feeding in both plants and BPH, besides enhancing available forms of major nutrients, namely nitrogen (N), phosphorus (P), potassium (K), and minor nutrients, namely calcium (Ca), magnesium (Mg) and sulphur (S), and Si in soil and rice plants. The antioxidative enzymes’ mediated plant defence and positive alteration of the nutrient composition of soil along with other reported plant defences, namely callose deposition, silicification, and positive alteration of photosynthesis-related parameters, indicated Si amendment as a potential alternative strategy for BPH management under climate change conditions.