Foliar application of folic acid in modulation of growth and biochemical attributes of garlic (Allium sativum L.) under salt stress

Salinity is one of the major abiotic stresses limiting crop productivity worldwide. According to the Food and Agriculture Organization (FAO, 2021), approximately 833 million hectares of soil are affected by salinity globally. A pot experiment (3 salinity levels × 4 folic acid concentrations; 3 replicates) was carried out at the Botanical Garden, University of Education, Vehari, to test whether foliar folic acid (FA; 0, 0.2, 0.4, 0.6 mM) improves garlic performance under 0, 50 and 100 mM NaCl. Key morphological and biochemical traits were measured three weeks after treatments. Two-way ANOVA showed significant effects of salinity and FA on growth and biochemical parameters. Under non-saline conditions, foliar FA at 0.6 mM increased root length from about 11 cm (control) to 23 cm. Even at 100 mM NaCl, FA maintained root length around 20 cm compared with 12 cm in untreated plants. Shoot fresh weight at 100 mM NaCl increased from about 13.5 g (control) to 21 g with FA (≈56% improvement). Salt stress increased malondialdehyde (MDA) to nearly 2.8 nmol g⁻¹ FW, but foliar FA reduced it to ~1.5 nmol g⁻¹ FW. Antioxidant enzymes also responded strongly: catalase activity under 100 mM NaCl rose from ~20 U mg⁻¹ protein (control) to ~38 U mg⁻¹ protein with FA. Total soluble sugars also increased with FA, particularly at 0.6 mM. These results indicate that foliar FA, especially 0.6 mM, mitigates salt-induced damage and improves growth and biochemical resilience of garlic under controlled pot conditions. This study provides novel evidence that FA can serve as a low-cost foliar amendment for enhancing salt stress tolerance in garlic.