Impact of salinity and media on growth and flowering of a hybrid Phalaenopsis orchid

The effects of water salinity [0.05, 0.40, 0.75, 1.10, and 1.40 dS . m(-1) of electrical conductivity (EC)] on Phalaenopsis orchids grown in 100% fine-grade fir bark or a combination of 80% bark and 20% sphagnum peat were studied. In both media, flower diameter decreased slightly as salinity increased. Plants in bark had more flowers as salinity increased, but had fewer flowers than those grown in bark/peat. In either medium, salinity had no effect on the number of new leaves produced. As salinity increased, plants in bark had increasingly larger total leaf area, with a maximum at EC = 1.10 dS . m(-1). Leaf area of plants in bark/peat was greater than that of those in bark, but was unaffected by salinity. Root fresh mass was lower with increasing salinity in both media. Media had no effect on mineral concentration in the leaf. In bark, increasing salinity increased the Ca and Na concentrations but had no effect on the concentration of other minerals in leaves. As salinity increased in the bark/peat medium, leaf concentrations of P, Fe, and Cu decreased and those of K, Ca, Mg, Na, and Zn increased, but the concentration of N was unaffected by salinity. Leachate from bark/peat had twice the EC and lower pH (4.9) than bark (5.7).