Sodium‐induced calcium deficiency in salt‐stressed corn

Abstract The effect of the Na + /Ca 2+ ratio in the root media on salt‐stressed corn ( Zea mays L. cvs DeKalb XL‐75 and Pioneer 3906) was determined in greenhouse experiments. Plants grown in a complete nutrient solution salinized with 86.5 mol m −3 NaCl exhibited severe Ca 2+ deficiency symptoms at the four‐leaf stage. The symptoms disappeared when part of the NaCl was replaced with 10 mol m −3 CaCl 2 (Na + /Ca 2+ molar ratio = 5.7). Salt stress at an iso‐osmotic potential of −0.4 MPa substantially decreased shoot growth at all solution Na + /Ca 2+ ratios from 34.6 to 0.26. However, the dry weights of blades at 26 d of age were much less when plants were salinized with NaCl alone, particularly that of DeKalb XL‐75 which was more susceptible to Na‐induced Ca 2+ deficiency than was Pioneer 3906. The growth of sheaths was similarity reduced by sail stress at all Na + /Ca 2+ ratios. The symptoms of Ca 2+ deficiency were correlated with low Ca 2+ concentrations in the leaf tissue. Ca 2+ concentrations in the developing blades of NaCl‐stressed plants were much lower than in control plants. As the Na + /Ca 2+ ratio in the solution was decreased, Ca 2+ levels increased in both the blades and sheaths while Na + concentrations greatly decreased. DeKalb XL‐75 was much less effective than Pioneer 3906 in restricting the uptake of Na + . The results clearly indicate that NaCl stress may cause lesions and unique plant responses that are not manifested on agronomic plants grown on saline soils.

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