Brassica metabolite priming boosts growth and ion-water homeostasis under salt stress in broccoli

Salt stress represents one of the most important abiotic stresses affecting crop yields globally. It interferes with plant development, productivity, and metabolic balance by causing both osmotic stress and ion toxicity. Recently, seed priming has gained recognition as a promising approach to improve plant tolerance to abiotic stress. This technique involves preconditioning seeds with natural or synthetic agents, triggering molecular and physiological modifications that generate a form of stress memory. In this research, we investigated the effects of seed priming with a glucosinolate-rich broccoli (Brassica oleracea L. var. italica) extract on broccoli plants grown under control and salt stress conditions (80 mM NaCl). For this purpose, a combination of physiological (growth, photosynthetic activity, water status), biochemical (ionomic and metabolite profiling), and transcriptomic (RNA-seq) analyses was performed on adult plants to uncover the mechanisms underlying the response to treatment. Our results demonstrate a dual effect: the extract acted as a biostimulant under non-saline conditions, while functioning as a priming agent under salinity. Broccoli extract increases biomass and enhances plant performance and water transport capacity under both conditions. Photosynthetic efficiency improved under non-saline conditions, as evidenced by increased transpiration, stomatal conductance, and internal CO₂ concentration. At the transcriptomic level, primed plants exhibited repression of stress-related genes and upregulation of pathways related to growth and hormone signalling. Under salinity, root tissues displayed dynamic transcriptional reprogramming involving hormonal crosstalk (ABA), aquaporin modulation (PIP2;1, PIP2;2, TIP2;1), activation of ion transporters (NCL, CCX2, SOS2), and regulated secondary metabolism, including glucosinolate transport. These results suggest that seed priming with broccoli extract promotes a more efficient and balanced stress response, supporting both resilience and sustained development.