Agronomical and physiological responses of containerized ornamentals to salinity induced by major nutrients

High concentration of nutrients in the irrigation water of greenhouse crops is a typical phenomenon of the south Mediterranean areas and has often negative effects on plant growth and yield. High values of electrical conductivity (EC) of nutrient solution (NS) may lead to an excess of some ions and consequently to physiological and biochemical stresses resulting in reduced plant growth, leaf chlorosis and abscission. In order to evaluate the effects of increasing EC of irrigation water on plant growth and quality, a greenhouse cultivation of three containerized ornamental species (Asteriscus maritimus L., Euphorbia × lomi Rauh and Murraya paniculata (L.) Jacq.) was carried out in 7L pots containing a mixture of Mediterranean red soil, black peat and perlite (1:1:1, v/v/v). Three levels of EC (2.0, 4.0 and 6.0 dS m^-1) were applied to plants by increasing macro and micronutrients content of the NS. For each species, morphological and physiological parameters were monitored during growing cycle. Asteriscus was the most tolerant of the three tested species to the high nutrients concentration of NS as best performances were recorded in plants grown with maximum EC level while lowest values were measured in the control (2.0 dS m^-1). Euphorbia and Murraya presented medium tolerance to the salinity induced by major nutrients as plants of both species did not show significant differences among treatments on main morphological and physiological parameters, with no or limited reduction of ornamental traits as the EC of the NS was increased.