Effects of low iron stress on growth, antioxidant, and photosynthetic physiological characteristics of maize cultivar with contrast iron efficiency

When corn is deficient in iron, its leaves lose their green and yellow color, its growth is retarded, and heading ceases, resulting in reduced production. Previous studies on the response of corn genotypes to low iron stress have mostly focused on the differences in root morphology, absorption efficiency, and material production. Studies on the effects of low iron stress on the antioxidant and photosynthetic physiological characteristics of corn varieties with different iron efficiencies are not common. This study adopted different iron efficiency corn varieties as experimental material to analyze oxidation resistance and photosynthetic physiological characteristics of corn seedlings under low iron stress. The study aimed at to identify iron efficient mechanism of different corn varieties to lay the theoretical foundation and develop technical support for corn cultivation. Corn varieties with high iron efficiency (ZH 2; ZD 619) and iron low efficiency (CD 418; XY 508) were tested at three concentrations of pure iron (Fe0: 0 μmol∙L⁻¹; Fe10: 10 μmol∙L⁻¹; Fe100: 100 μmol∙L⁻¹), and the effects of low iron stress on seedling growth and antioxidant and photosynthetic physiological characteristics of corn varieties with different iron efficiencies were studied. The results showed that plant height, stem diameter, leaf area, net photosynthetic rate, stomatal conductance, transpiration rate, aboveground dry matter and iron accumulation and allocation ratio, dry matter weight per plant, and iron accumulation in corn seedlings decreased significantly under low iron stress, whereas the intercellular CO₂ concentration, peroxidase (POD) activity, contetns of malondialdehyde (MDA), soluble sugar, proline and soluble protein, root dry matter and iron accumulation ratio, root shoot ratio, and root shoot iron ratio were significantly increased. However, the morphological characteristics, photosynthetic characteristics, accumulation and distribution of dry matter and iron, and MDA content of iron-efficient varieties were lower than those of iron-inefficient varieties. The increase in osmotic regulation substances contents and POD activity was higher than that of iron-inefficient varieties, and the difference amplitude between the two varieties increased with the increase in stress. Correlation analysis showed that iron accumulation in corn seedlings was positively correlated with plant height, stem diameter, leaf area, and dry matter, and negatively correlated with the root-to-shoot ratio and root-to-shoot iron ratio, among which the correlation with dry matter (R²=0.9811) was the strongest. Comprehensive analysis showed that, compared with iron-inefficient varieties, iron efficient varieties under the stress of low iron have high osmotic regulation substances contents and antioxidant enzyme activity, which is beneficial for reducing membrane lipid peroxidation damage, maintaining high photosynthetic characteristics, accumulation and distribution of underground material and iron, and maintaining aboveground growth, so as to improve its adaptability to low iron environment.