In this preliminary study, we evaluated the salinity tolerance of selected herbaceous perennials. Liners of Rudbeckia hirta `Becky Orange', Phlox paniculata `John Fanick', Coreopsis grandiflora `Early Sunrise', Lantana ×hybrida `New Gold' and Cuphea hyssopifolia `Allyson' were transplanted to 4-gal plastic containers filled with peat moss: pine bark: sand (3:1:1) medium amended with dolomite, Micromax and Osmocote 18-6-12 (at 2, 0.6, and 6 kg·m3, respectively). The plants were irrigated for 14 weeks with tap water containing 0, 1.5, 3, 6, 12, and 24 mM of NaCl: CaCl2 salt mixture (2:1 molar ratio). Increasing salt stress had differential effects on plant growth and quality, with Rudbeckia and Phlox being the most adversely affected even by the lowest salt treatment of 1.5 mM, with dry weight reductions of ∼25% compared to the controls. Conversely, Lantana and Cuphea tolerated extremely well salinity up to 12 mM, where dry weight reductions were less than 10% of the nonsalinized controls. The Lantana and Cuphea plants also presented the lowest leaf Cl accumulation with increasing salinity, whereas Coreopsis showed the highest Cl accumulations at any salinity level. Plots of leaf Cl concentration against dry weights showed steeply declining relationships for Rudbeckia and Phlox plants, confirming our observations and assessment that these species are to be considered salt-sensitive. Leaf Na accumulation is currently being analyzed.
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