Salinity is an abiotic stressor that severely limits rice productivity worldwide by inducing osmotic stress and ionic toxicity. This study aimed to evaluate the ameliorative effects of foliar-applied salicylic acid (SA) on the root anatomical characteristics of three rice cultivars with varying sensitivity: pigmented rice ‘Sembada Hitam’ (pigmented), compared to white rice ‘Ciherang’ (moderately tolerant), and ‘IR-64’ (sensitive). The role of exogenous SA in mitigating salinity stress in rice is well-documented regarding shoot biomass, ion homeostasis and antioxidant defense mechanisms, its explicit impact on internal root anatomical plasticity remains poorly understood. The plants were grown in a soil-compost medium (3:1) and subjected to 100 mM NaCl stress starting at 30 days after planting (DAP). Salicylic acid (1 mM) was applied foliarly at 25, 50, 75, and 90 DAP. Root anatomical parameters, including root diameter (RD), cross-sectional area (CSA), cortical radius (CR), and metaxylem characteristics, were observed through transverse sections at the end of the vegetative phase. This study established a definitive link between foliar-applied SA and the preservation of critical root microstructures. The results indicated that salinity stress significantly reduced RD, CSA, CR, and stele across all cultivars. The sensitive cultivar ‘IR-64’ exhibited the most pronounced anatomical degradation, particularly in sclerenchyma thickness and metaxylem development. Conversely, ‘Ciherang’ showed higher structural resilience under saline conditions. The application of 1 mM SA successfully mitigated these negative impacts, particularly in ‘IR-64’ by significantly increasing root diameter, cortical radius, and the number and diameter of metaxylem vessels. This study concluded that exogenous SA application is an effective strategy to enhance the salt tolerance of rice by preserving critical root anatomical integrity.
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