Salicylic acid enhances growth and ionic balance of shallots (Allium ascalonicum L.) grown from true seeds under saline conditions

Salinity stress is a significant limiting factor in shallot (Allium ascalonicum L.) production, affecting ion homeostasis and plant growth. This study aimed to evaluate the role of salicylic acid (SA) in enhancing salt tolerance in shallots grown from true shallot seeds (TSS) under medium saline conditions maintained at ± 5.8 dS/m. A factorial experiment was conducted using a randomized block design with four SA concentrations (0, 1, 1.5, and 2 mM) and three transplanting ages (28, 35, and 42 days after sowing). Saline conditions were induced by applying 2,922 ppm NaCl (equivalent to 5.8 dS/m) to the growing medium every five days, starting at 10 days after planting (DAP). SA was administered by spraying it onto the leaves at 14, 17, 20, and 23 DAP. The results of the study show that the SA application significantly influences Na⁺ and K⁺ uptake of shallot plants grown in saline conditions of 5.8dS/m, reducing Na⁺ accumulation while increasing K⁺ content in plant tissues. The Na⁺/K⁺ selective absorption index (SAI) also decreased below 1.0 in the 1–1.5 mM SA treatments, indicating improved ionic balance and stress tolerance. The 1.5 mM SA concentration resulted in the highest bulb dry weight (12.07 g), stover dry weight (25.92 g), and bulb number per plant (3.89). Moreover, it produced the highest proportion of Grade 1 bulbs (78.17%) as per the Indonesian National Standard (SNI 3159:2013). Early transplanting at 28 DAS further improved yield parameters. These findings suggest that moderate SA application, particularly at 1.5 mM, can mitigate salinity stress and enhance productivity in shallot cultivation by improving ion regulation and physiological performance.