Comparative Analysis of Morphological Responses in Rice Genotypes under Salinity Stress at the Seedling Stage

Aims: To evaluate the morphological responses of contrasting rice genotypes under varying EC levels and identify the EC concentration at which the genotypes exhibit minimal adverse effects. Methodology: FL478 (salt-tolerant) and BPT5204 (salt-susceptible) genotypes were evaluated under a completely randomized design (CRD) with three replications. Seedlings were exposed to salinity levels ranging from 0 to 12 dS/m for 7 days at the seedling stage. Morpho-physiological traits including shoot length (SL), root length (RL), shoot-to-root ratio (SLR), fresh weight (FW), dry weight (DW), water content (WC), total shoot length (TSL), and dry matter content (DMC) were measured. Significant differences from the control were assessed using Dunnett’s test. Results: A significant reduction was observed in shoot length (SL), shoot-to-root length ratio (SLR), fresh weight (FW), total shoot length (TSL), and water content percentage (WC), along with fluctuations in root length (RL) and dry weight (DW). However, dry matter content (DMC) increased with increasing salinity levels. Among the two genotypes, the susceptible BPT5204 exhibited a greater percentage of reduction in trait values compared to the tolerant FL478. Conclusion: Salinity levels of 2-4 dS/m caused only minor physiological changes, with no significant differences from the control in most traits, indicating their potential as effective priming treatments. From 5 dS/m onwards, significant growth impairments were observed. Notably, a hormetic response was evident at 11 dS/m, where both BPT5204 and FL478 showed greater growth inhibition than at higher salinity levels, suggesting a complex, non-linear relationship between salinity and plant performance. Correlation analysis further revealed strong negative associations between salinity and key morpho-physiological traits, underscoring the inhibitory impact of elevated electrical conductivity (EC) on plant growth.