Abstract

Urban salinization from NaCl de-icing threatens ornamental plants along roadsides by disrupting growth and esthetic quality. This study evaluated salt tolerance thresholds in Gazania splendens L. and Dianthus caryophyllus L., two popular bedding species, to guide sustainable urban landscaping. Seedlings grown from certified seeds were subjected to NaCl treatments (0, 3, 6, 9 g L−1) in 2 L pots under greenhouse conditions, with growth traits, biomass, photosynthetic pigments, and antioxidants assessed. Salinity reduced leaf number at 9 g L−1 in both species and root elongation primarily in G. splendens, alongside biomass declines. G. splendens showed increased chlorophyll a, chlorophyll b, carotenoids at moderate stress, as well as total phenolic content, ferric-reducing antioxidant power, and ABTS radical scavenging capacity at high salinity. D. caryophyllus showed pigment declines and stable antioxidants. Principal component analysis separated species and treatments. Under the conditions of the present study, both species maintained satisfactory performance at salinity levels up to 3 g L−1 NaCl. G. splendens exhibited superior antioxidant acclimation despite greater growth sensitivity, whereas D. caryophyllus maintained photosynthetic pigment contents, providing useful information for the selection of ornamental species suitable for saline urban environments.

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