Silicon and Boron on the C:N:P Homeostasis and Nutrient Use Efficiency in Cotton Flowers to Alleviate Boron Deficiency

This study aimed to investigate the effects of boron (B) deficiency on the stoichiometric balance of carbon (C), nitrogen (N), and phosphorus (P) in cotton flowers and to evaluate whether isolated or combined foliar applications of B and silicon (Si) can ameliorate these imbalances. Five treatments were established: B sufficiency, B deficiency without spraying, B deficiency with B spraying (1.5 g L⁻¹), B deficiency with Si spraying (1.0 g L⁻¹), and B deficiency with combined B + Si spraying (1.5 g L⁻¹ B + 1.0 g L⁻¹ Si), each with ten replicates. The results demonstrated that B concentration was significantly higher in cotton flowers under the B-sufficient treatment compared to the other treatments. Boron deficiency induced a nutritional imbalance by reducing the CN and C:P stoichiometric ratios and decreasing the dry mass of all floral structures. Moreover, Si application, either alone or in combination with B, restored stoichiometric homeostasis, improving the utilization efficiency of C, N, P, and B, and increasing the dry mass of bracts, petals, and styles + stigmas. This study contributes to a deeper understanding of the effects of B deficiency in cotton flowers and highlights the importance of combined foliar applications of B and Si during the reproductive phase to enhance cotton cultivation.