Physiological and Biochemical Responses of Maize (Zea mays L.) Cultivars to Salinity Stress
Abstract
Salinity is a critical abiotic constraint to maize (Zea mays L.) production, affecting growth, photosynthesis and oxidative balance. This study examined the responses of five cultivars (DHM 144, NK 7720, SY 594, Sunny NMH 777 and Dragon NMH 1247) to 150 mM NaCl stress. Measurements at 0, 7 and 14 days after stress initiation included plant height, leaf area, chlorophyll content, stomatal conductance, antioxidant enzyme activities [superoxide dismutase (SOD), catalase (CAT), peroxidase (POD)], proline accumulation and malondialdehyde (MDA) levels. Salinity reduced morphological and physiological traits across genotypes, with Dragon NMH 1247 maintaining higher growth, chlorophyll content and stomatal conductance, coupled with enhanced SOD, CAT and POD activities and lower MDA accumulation. All cultivars had a higher proline content which was not always correlated with stress tolerance. Findings show that antioxidant capacity, chlorophyll retention and low oxidative damage are some of the main factors that determine salinity tolerance in maize. Dragon NMH 1247 emerged as the most tolerant genotype and is an attractive target for saline-prone environments and breeding programs.
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Introduction
Maize (Zea mays L.) is a universally significant cereal crop that is a staple food for millions of people, a critical component of livestock feed and a primary industrial raw material. Its capacity for adaptation to different agro-climatic factors has enabled its cultivation in different geographical areas, making it among the most extensively grown crops in the world (FAO, 2020). Nevertheless, its productivity is under threat from various abiotic stresses, especially salinity, which poses a considerable challenge to agricultural sustainability and food security.
Salinity stress negatively impacts plant growth and metabolism by interfering with water uptake, resulting in ionic toxicity and oxidative stress. These effects inhibit photosynthesis, nutrient assimilation and enzyme activity, ultimately leading to reduced yields (Munns and Tester, 2008). Even moderate levels of salt can cause significant losses in physiological performance and biomass gain in glycophytic crops such as maize, which is moderately sensitive to salinity (Cairns et al., 2013).
At the physiological level, salt stress affects plant height, leaf area, stomatal conductance and chlorophyll content— parameters used to measure plant vigor and photosynthetic performance under stress conditions. For example, reduction in stomatal conductance limits CO₂ uptake, thereby decreasing carbon assimilation and plant productivity (Zhang et al., 2006). Simultaneously, ionic and osmotic stress caused by salt induces symptoms including leaf chlorosis and stunted growth. At the biochemical level, salinity causes excessive production of reactive oxygen species (ROS), leading to oxidative stress on cellular components.
Conclusion
Salinity stress significantly impacted physiological and biochemical characteristics in maize, with considerable genotypic variation among the five cultivars evaluated. Dragon NMH 1247 demonstrated the highest salt tolerance, maintaining superior growth, chlorophyll content, stomatal conductance and antioxidant enzyme activities while accumulating less MDA. Sunny NMH 777 and SY 594 were more sensitive, exhibiting greater growth reduction, chlorophyll degradation, weaker antioxidant responses and higher oxidative damage. DHM 144 and NK 7720 showed intermediate tolerance levels.
The findings indicate that effective salinity tolerance in maize requires integrated mechanisms including sustained photosynthetic pigment retention, modulated stomatal behavior, coordinated antioxidant enzyme activity and membrane stability. Proline accumulation, while universally induced by salinity, does not independently confer tolerance and may reflect stress intensity rather than adaptive capacity in sensitive genotypes.
Dragon NMH 1247 represents a promising genetic resource for cultivation in saline-prone areas and for inclusion in breeding programs aimed at developing salt-tolerant maize varieties. Further research should investigate the molecular mechanisms underlying the superior performance of this cultivar, including expression patterns of stress-responsive genes and ion transport regulation. Field validation under diverse saline conditions would also be valuable to confirm the consistency of these findings across environments.
References
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