Seaweed-based biostimulant alleviates cadmium-induced physiological stress in tomato (Solanum lycopersicum L.)

Abstract Background Cadmium (Cd) contamination, primarily from anthropogenic activities, represents a major concern that threatens plant productivity and food safety by promoting bioaccumulation in edible plant tissues. Tomatoes (Solanum lycopersicum L.), a globally important horticultural crop and a model species, are notably susceptible to heavy metal uptake. Sustainable strategies to increase plant resilience in this context are urgently needed. This study evaluated the effectiveness of a seaweed-derived biostimulant, ProSoil Recover (PSR), in mitigating Cd toxicity, focusing on growth parameters, Cd uptake, the translocation factor, bioaccumulation, and the quantification of physiological responses, such as total chlorophyll content, nitrate reductase enzymatic activity, proline content and peroxidase enzymatic activity, in tomato plants grown in a soilless culture system to evaluate the consequences of Cd-induced abiotic stress at the macroscopic and biochemical levels. Results The tomato plants were subjected to five different Cd concentrations, with or without PSR application, under a factorial arrangement experimental design. The growth parameters were not negatively affected by Cd exposure. Cd uptake increased proportionally with increasing external Cd supply (p < 0.0001), and it was distributed at higher and similar levels in roots (44.73%) and leaves (49.12%) and much lower in fruits (6.15%). Cd uptake in all organs was significantly negatively correlated with the translocation factor (p < 0.0001). In the leaves, Cd stress significantly reduced the total chlorophyll content (˗14.75%) but promoted increases in nitrate reductase activity (+ 61.04%). Moreover, compared with the control plants, the Cd-supplemented plants presented increased proline content (+ 105.42%) and peroxidase activity (+ 58.27%), which are indicators of oxidative stress. PSR application consistently reduced average Cd uptake in roots (˗32.48%), leaves (˗30.47%) and fruits (˗34.82%), lowered the bioaccumulation index (˗35.43%), and increased the translocation factor (+ 76.43%). In most cases, the PSR-treated plants presented attenuated oxidative stress, as evidenced by a reduced proline content (˗12.7%) and peroxidase activity (˗23.96%). Conclusions Seaweed-based biostimulants such as PSR offer a promising strategy to alleviate heavy metal-induced abiotic stress in horticultural crops. By reducing Cd bioaccumulation, increasing the translocation factor, modulating key physiological responses, and mitigating oxidative damage, the PSR contributes to safer food production and promotes sustainable agricultural practices under environmental stress conditions.