Diatom contained alginate-chitosan hydrogel beads with enhanced hydrogen bonds and ionic interactions for extended release of gibberellic acid.

Hydrogels in agriculture offer controlled release, however, face issues with rapid disintegration, swift release, and inability to protect active ingredients. To overcome this, the study presents a hydrogel delivery system that uses dopamine-functionalized nanoporous diatom (DE-PDA) microparticles entrapped in alginate and chitosan matrices to deliver plant growth hormone, gibberellic acid (GA) that suffers from instability, limiting its field application. Developed GA@hydrogel beads exhibited an encapsulation efficiency of 85.2 % and demonstrated thermal and functional properties that suggested complex interactions between biopolymers. They showed enhanced stability, retention, and extended release for GA, improving tomato seed germination and plant growth. The GA release was governed by Fickian diffusion and the polymer relaxation with 86.3 % release by the 15th day, with a high swelling rate compared to a system without DE-PDA that only sustained GA release for 5 h. The GA@hydrogel system boosts tomato seed germination rates to 100 % on the third day for a 0.05 % GA@hydrogel formulation, demonstrating enhanced seedling growth. Also, they prove more effective than free GA in increasing the physiological parameters of tomato plants. Further, the pot experiments show enhanced plant growth, suggesting a new trend of GA delivery to plants through soil.