Calcium Ion Richness in Cornus hongkongensis subsp. elegans (W. P. Fang et Y. T. Hsieh) Q. Y. Xiang Could Enhance Its Salinity Tolerance

Abstract

Cornus hongkongensis subsp. elegans (W. P. Fang et Y. T. Hsieh) Q. Y. Xiang has attracted much attention for its potential ornamental value and extensive adaptation to heterogeneous environments. In this study, seedlings were treated with four sea salt concentrations (0 (S0), 0.2 (S2), 0.3 (S3), and 0.4% (S4), w/w) by hydroponics. We determined that the degree of injury symptoms in the salinized seedlings increased with the rising salt concentration and with the extent of stress duration. Calcium ion (Ca2+) concentrations reached peaks of 22.00, 17.05, and 12.77 mg g−1 in the leaves, stem, and root in the S4 treatment, respectively. As the salt concentration rose, calcium oxalate crystals in leaves were mainly enriched in the abaxial parenchyma of the main vein, as well as the palisade tissues and their junction with the spongy tissues of the mesophyll. The density of calcium oxalate crystals increased almost 1.6-fold in the leaves in the S4 treatment compared to the S0 treatment. Our results suggest that C. elegans could be cultivated in coastal areas with a salt concentration of 0.2%–0.3% in eastern China. In addition, a high Ca2+ supply in the field may be an effective strategy to enhance salinity tolerance in dogwoods.