Abstract
Background Exploring the adaptive responses of onions (Allium cepa L.) to salinity reveals a critical challenge for this salt-sensitive crop. While previous studies have concentrated on the effects of sodium (Na+), this research highlights the substantial yet less-explored impact of chloride (Cl−) accumulation. Two onion varieties were subjected to treatments with different sodium and chloride containing salts to observe early metabolic responses without causing toxicity.Results The concentrations of both ions were increased; with Cl− exhibiting a more pronounced effect on metabolic profiles than Na+. Onions adapt to salinity by altering organic acid concentrations, which are critical for essential functions such as energy production and stress response. The landrace Birnförmige exhibited more effective regulation of its Na+/K+ balance and a milder response to Cl− compared to the hybrid Hytech. Metabolic alterations were analyzed using advanced techniques, revealing specific responses in leaves and bulbs to Cl− and Na+ accumulation.Conclusion The comprehensive study provides new insights into onion ion regulation and stress adaptation, emphasizing the importance of considering both ions, Na+ and Cl− when assessing plant responses to salinity.