Differential Growth, Quality and Nutrient Responses of Azalea Hybrids to Salinity

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  • 1 Texas A&M Univ., Horticultural Sciences, Dallas, TX 75252

The azalea hybrids `Delaware Valley White' (`DVW') and `Hershey Red' (`HR') were grown in 7-L containers filled with a 4 sphagnum peat: 2 pine bark: 1 sand medium (v/v) and fertigated for 15 weeks with a complete nutrient solution supplemented with 0, 6 and 12 mm NaCl-CaCl2 (2:1 molar ratio). Regardless of salinity stress, `DVW' plants had dry weights and leaf areas significantly higher (by 24.7% and 10.2%, respectively) than in `HR' plants. Salinity, however, caused differential growth and quality responses between the hybrids. Growth in `DVW' plants decreased with salinity increases, with 22.6% and 32.4% reductions in total dry weight and leaf area, respectively, observed at 12 mm salt compared to controls. Conversely, `HR' plants exposed to 12 mm salt showed no differences in yield parameters with respect to the controls, whereas plants receiving 6 mm salt showed increases of 14.0% and 7.1% in total dry weight and leaf area, respectively, with respect to the controls. Plant quality, as assessed by visual symptoms of salt injury (“salt burn”), was significantly reduced by salinity increases in `DVW' plants, but was not affected in `HR' plants. While unaffected by salinity, leaf K status in `HR' plants was significantly lower than in `DVW', which showed increases in K concentration with salinity increases. Leaf Ca, Cl and Na concentrations increased with added salinity in both hybrids. The `DVW' plants, however, accumulated exceedingly higher Cl and Na concentrations (up to 3.33% and 5,650 mg·L-1 respectively) than in `HR' plants (up to 1.31% and 463 mg·L-1, respectively). Only the yield and quality of `DVW' plants were negatively and significantly correlated to increases in leaf Cl and Na concentrations.

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