Biochemical and biomolecular response of Arabidopsis seedlings to osmotic and salt stress: Mitigation by biostimulant formulation enriched in betalain degradation products

Abiotic stress, such as salt and osmotic stress, negatively impacts plant growth and productivity, making it crucial to explore sustainable solutions that can improve plant resilience. In this study, we investigated the effects of a biostimulant formulation containing betalain degradation products (BDPs) on the growth and stress resistance of Arabidopsis thaliana seedlings subjected to salt stress (SS) and osmotic stress (OS) conditions. Specifically, we fortified the medium culture of stressed seedlings with 0.02, 0.10, and 0.20 mg/mL of BDPs-enriched biostimulant, revealing significant improvements in growth and biomass under both SS and OS conditions, with the most notable effects in OS condition. In this study, we applied these findings to stress conditions, demonstrating that treatment with the formulation containing BDP-related compounds significantly enhanced seedling growth and biomass in both salt stress (SS) and osmotic stress (OS) environments, with the most significant effects observed in OS conditions. Specifically, seedlings treated with 0.20 mg/mL of BDP-enriched biostimulant exhibited growth increases of up to 150 % under OS conditions and a 116 % increase under SS conditions, restoring growth metrics comparable to control conditions. We analyzed the impact of the formulation on the dynamics of reactive oxygen species (ROS) and the activities of antioxidant enzyme, revealing that BDPcontaining formulation effectively balanced ROS levels by modulating superoxide dismutase (SOD), catalase (CAT) and the glutathione peroxidase-glutathione reductase (GPX-GR) system in both stress conditions. Furthermore, BDP-containing formulation affected proline metabolism by reducing its accumulation under stress conditions and enhancing proline catabolism, as demonstrated by the upregulation of the genes for proline dehydrogenase (PDH), pyrroline-5-carboxylate dehydrogenase (P5CDH), and ornithine aminotransferase (OAT). These findings suggest that the biostimulant enriched in BDP-related compounds enhanced the resilience of Arabidopsis seedlings to abiotic stress by regulating both oxidative stress responses and proline metabolism, highlighting their potential applications for improving crop tolerance to challenging environmental conditions.