Early-stage morpho-physiological and ionic responses of commercial maize hybrids to graded salinity stress

Soil salinity restricts maize establishment by reducing germination, seedling expansion, biomass formation, and ionic balance, making graded early-stage screening important for salt-affected crop production. However, integrated evidence combining morphological, physiological, and ionic traits of commercial maize hybrids from sowing through early establishment remains limited. This study provides an integrated comparison of PAC 999, PAC 139, KING CORN, and PAC 339 under 0, 2, 4, 8, and 10 dS m −1 salinity in a 4 × 5 × 3 factorial pot experiment with four replications, giving 240 experimental units. Salinity was imposed from sowing, and destructive harvests were conducted at 7, 14, and 21 days after salinity imposition. Germination, growth, biomass, survival, chlorophyll, proline, Na + , K + , and Na + /K + ratio were analyzed using pot-level data, factorial models, GLMs, and exploratory PCA. Germination declined from 89.88% at 0 dS m −1 to 63.61% at 10 dS m −1 , and germination vigor index decreased from 1553.04 to 649.33. At 21 DAS, plant height declined from 24.46 to 14.78 cm plant −1 , seedling length from 44.18 to 26.46 cm plant −1 , and whole-plant dry weight from 4.108 to 2.469 g plant −1 ; survival was lowest at 10 dS m −1 . Chlorophyll a decreased from 1.581 to 1.298 mg g −1 FW, whereas proline increased from 3.200 to 13.284 µmol g −1 FW. At 8–10 dS m −1 , PAC 999 consistently maintained lower shoot Na + accumulation or Na + /K + ratio than PAC 139 and KING CORN, while PAC 339 showed a similar advantage in selected high-salinity comparisons. PCA explained 76.32–79.48% of PC1 variance and separated growth, biomass, chlorophyll, and K + traits from Na + and proline responses. Overall, the trait pattern identified PAC 999 and PAC 339 as stronger early-stage candidates under the semi-controlled conditions, supporting SDG 2 and 13-relevant trait-based screening for sustainable and climate-resilient maize evaluation, although field validation is required before agronomic recommendations.