Early-season maize responses to salt stress: Morpho-physiological, leaf reflectance, and mineral composition

Salt stress is a major environmental factor that affects maize production. The impact of salt stress during the early vegetative stage inhibits growth and development. In this study, two maize hybrids, A6659 and P1316, were subjected to five salinity treatments with electrical conductivity 0, 3, 6, 9, and 12 dS m(-1) for 28 days. A total of 26 traits were evaluated, including morpho-physiological, biomass, leaf reflectance, and mineral composition in two independent studies. Under salt stress, stomatal conductance and transpiration were reduced, resulting in a canopy temperature rise of 4 degrees C. A higher salinity level (12 dS m(-1)) reduced plant height (47%) and total leaf area (44%), consequently reducing total shoot dry weight (37%) and total root dry weight (24%). Leaf minerals such as potassium, magnesium, and phosphorous declined with increasing salt concentrations. The elevated salt concentration in the rhizosphere caused an increase in leaf reflectance at the near-infrared (NIR) region, which is attributed to macronutrient deficiency under stress conditions. The results demonstrated that maize could withstand salt stress up to 3 dS m(-1), beyond which plant performance declines depending on the genetics. This study provides insights into key traits that can be used for screening or breeding maize for early-season salt stress tolerance.