Salt tolerance of flower crops grown in soilless culture

Gerbera, carnation, rose, aster, bouvardia, and lily were grown in a hydroponic system at different levels of salinity. The EC and sodium (Na) and chloride (Cl) concentrations maintained in the root environment solution were tuned at the expected salt sensitivity of the crops grown. The target values for the EC were between 1.7 and 5.2 dS m(-1) (25 degrees C) and the Na and Cl concentrations between 0 and 30 mmol L(-1). All experiments had one treatment in which the EC was increased through addition of nutrients instead of sodium chloride (NaCl). The calculated salinity threshold values were between 1.1 and 4.3 dS m(-1) and the salinity yield decrease (SYD) values between 2.1 and 16.8% per dS m(-1). For aster no values could be calculated, because the highest EC value of 4.2 in this experiment did not affect the production level. However, the regrowth of this crop after the first harvest was strongly hindered by the EC in the root environment, especially when the EC was increased with NaCl. The flower production of the bouvardia crop was specifically decreased by the addition of Na. Postharvest quality characteristics of the flower crops were not affected by the treatments. The relationships between the Na and Cl concentrations in solution and the uptake concentrations of these elements was determined for the different crops. Mostly, a linear relationship was found, for Cl sometimes a curvilinear relationship showed a better fit.