Unraveling the phenotypic and metabolic responses induced by urea-encapsulated hydrogel beads on Brassica juncea (L.) Czern & Coss†

Hydrogels, three-dimensional polymeric networks capable of absorbing and retaining significant amounts of aqueous solution, offer a promising platform for controlled release of desired compounds. In this study, we explored the effects of urea delivery through galactoxyloglucan–sodium alginate hydrogels on the phenotypic and metabolic responses of Brassica juncea, a vital oilseed and vegetable crop. The experiments were conducted with four treatments: control (without hydrogel beads and urea), direct urea supplementation (U), hydrogel beads with urea (HBWU), and hydrogel beads without urea (HBWOU). Our findings revealed that HBWU-treated plants exhibited commendable plant growth with significantly higher chlorophyll content (11.06 mg/0.1 g) compared to the control (3.67 mg/0.1 g) and U-treated group (6.41 mg/0.1 g). Metabolic analysis identified 17 major intra-cellular metabolites involved in nitrogen metabolism. HBWU treatment significantly boosted nitrogen assimilation in plants, as evidenced by the upregulation of 9 metabolites. Furthermore, a proposed schematic diagram illustrates the HBWU induced-metabolic pathways and nitrogen metabolism in B. juncea. These findings demonstrate the potential of hydrogel-based controlled-release systems to enhance plant growth and nitrogen assimilation.