Comprehensively assessing the effects of exogenous proline on nutritional and flavour quality of celery (Apium graveolens L.) under salt stress

Salt stress is one of the constraints limiting high-yield and high-quality cultivation of vegetables, currently, the effect of exogenous proline on the quality of celery under salt stress is rarely reported. The study aimed to explore the comprehensive effects of exogenous proline application on the quality of celery (Apium graveolens L.) under salt stress. The affiliation function method was used to comprehensively analyze the effects of foliar application of 0.3 mM proline on celery mineral nutrients, amino acids, organic acids, nitrate, dietary fiber, and volatile components under 100 mM NaCl stress. Results showed that exogenous proline application inhibited Na content and nitrate enrichment in celery, and promoted the accumulation of other mineral elements (N, P, K, Ca, Mg, Cu, Fe, Mn and Zn), glycine, oxalic acid, malic acid, citric acid, lignin, dietary fiber, and aromatic compounds in leaves and petioles under salt stress. In addition, the results of a comprehensive evaluation analysis of the affiliation function indicated that the application of exogenous proline to salt-stressed seedlings was an effective treatment which significantly mitigated the salt-induced detrimental effects. Overall, exogenous proline played a positive role in regulating the balance of mineral elements, accumulation of glycine, accumulation of organic acids, and enrichment of aromatic substances in celery under salt stress. Results from this study provides a theoretical basis for cultivating cultivation of high quality celery under saline conditions.