Repurposing crop aerial parts to provide D-sorbitol for plant-specific growth

Agricultural systems generate billions of tons of high-moisture plant residues annually, leading to soil degradation and replanting failure—a critical bottleneck for global sustainability. Here, using watermelon as a representative model, our survey of representative watermelon-producing regions in China identified unsustainable crop residue management as a key driver of this ecological bottleneck. We developed a Lactiplantibacillus plantarum WCFS1-mediated rapid fermentation system with the aim of repurposing watermelon aerial parts to alleviate continuous cropping obstacles and promote sustainable waste recycling. We found that the fermentation liquid promotes Brassica rapa growth through its key metabolite D-sorbitol. To date, D-sorbitol has been characterized primarily in Rosaceae plants as a sucrose-like energy source and signaling molecule, whereas studies in other plant families have focused predominantly on its roles in osmotic-stress responses. Thus, leveraging an unprecedented cross-lineage experimental framework spanning dozens of cultivation trials, we systematically evaluated the effects of exogenous D-sorbitol across 32 phylogenetically representative plant species, including bryophytes, ferns, gymnosperms, and angiosperms. Excitingly, we discovered a previously unrecognized light intensity–sorbitol–starch cascade that affects energy metabolism and growth in angiosperms, particularly in Brassicaceae and Crassulaceae, while having no effect on the Rosaceae and Plantaginaceae. This mechanism spans the evolutionary lineage of true dicots. Additionally, we found that rapid fermentation reduces the inhibitory effects of allelotoxins from fresh watermelon stem and leaf on the growth and yield of Brassica rapa and Zea mays by significantly reducing allelochemical content in fresh tissues and markedly improving the composition of rhizosphere soil bacterial communities. Our work establishes a closed-loop, waste-to-growth strategy that transforms an ecological burden into a targeted agricultural input, providing a scalable solution for sustainable crop production.