Accelerated rapeseed germination and robust root growth facilitated by porous carbon within gellan gum hydrogel beads

Soilless cultivation using hydrogels as growth media offers significant water and fertilizer savings, reduces soil-borne diseases, and mitigates the limitations of traditional soil and hydroponic systems. This approach presents a promising path toward sustainable green agriculture. However, conventional hydrogel-based substrates are often bulky, translucent, and limited in functionality, which restricts root respiration and physiological activities while failing to mimic the microporous structure and environmental regulation of soil. To address these limitations, we incorporated carbon black (CB) into spherically structured hydroxyethyl cellulose-gellan gum (HG-C) hydrogel beads and developed a stacked hydrogel bead system to optimize the root growth environment. The addition of CB improved the temperature regulation capability, enhanced pore connectivity, increased specific surface area, and improved water retention while preventing root exposure to light. In rapeseed germination and growth experiments, the HG-C hydrogel substrate significantly enhanced growth metrics, including shoot length, root length, root surface area, and root volume. Notably, under low-temperature conditions, the HG-C hydrogel substrate effectively promoted root development, compared to hydrogel beads without CB, root length increased by 648 %. Therefore, HG-C hydrogel beads represent a novel growth substrate with immense potential for enhancing seedling growth and providing a new strategy for crop resilience under adverse environmental conditions.