Silicon Nanoparticles Modulate C:N:P Homeostasis and the Efficiencies of Nutrient Uptake, Translocation, and Use in Sugarcane Under Calcium Deficiency and Sufficiency.

Calcium (Ca) deficiency is a major nutritional constraint for sugarcane, impairing stoichiometric homeostasis and biomass accumulation. In this context, silicon dioxide nanoparticles (nSiO2) have emerged as a promising alternative due to their high reactivity and potential to modulate mineral homeostasis. This study evaluated the effects of nSiO2 on C:N:P:Si homeostasis and on nutrient uptake, translocation, and use efficiencies in sugarcane plants grown under Ca deficiency and sufficiency. The experiment was conducted in a greenhouse using a 2 × 2 factorial design, with two Ca conditions (0 and 3 mmol L-1) and two nSiO2 conditions (0 and 1.77 mmol L-1 of Si), with four replications. Calcium deficiency reduced nutrient accumulation and nutritional efficiencies of several macro- and micronutrients, disrupted stoichiometric ratios, and decreased shoot dry mass. The application of nSiO2 under Ca deficiency increased Si concentration and accumulation along with other nutrients, reduced C:Si ratios, enhanced nutrient uptake, translocation, and use efficiencies, and resulted in increased shoot biomass. Under Ca-sufficient conditions, nSiO2 promoted nutritional adjustments and improved nutrient efficiencies but did not affect biomass production. Overall, the results demonstrate that nSiO2 acts as a nutritional modulator and is more effective in mitigating the adverse effects of Ca deficiency through stoichiometric rebalancing and improved nutrient use efficiencies.