Effects of salinity on the germination, growth, and nitrate contents of purslane (Portulaca oleracea L.) cultivated under different climatic conditions

Interest in cultivating purslane (Portulaca oleracea L.) as a food crop has increased since its identification as an excellent source of some biologically-active compounds that are considered to be essential for the promotion of human health and the prevention of disease.The aim of this research was to determine the effects of salinity, by means of exposure to different concentrations of NaCl in the nutrient solution, on the germination, growth, yield, and nitrate contents of purslane cultivated in a hydroponic system under two different light intensities. The results indicated that higher germination percentages (approx. 50%) were obtained between saline levels with electrical conductivities (EC) of 0 - 12.5 dS m-1. Above 12.5 dS m-1, the germination percentage decreased significantly. Salinity reduced both shoot and root growth. This reduction was greater in plants grown under the lower light intensity. When the EC of the nutrient solution increased from 2.5 dS m-1 to 15.0 dS m-1, yields were reduced by 26% in plants grown in a greenhouse, and by 82.2% in plants grown under the lower light intensity in a growth chamber. In both cases, nitrate levels increased in plants grown at an EC of 5.0 dS m-1, but nitrate levels decreased with further increases in salinity. In all cases, nitrate levels were below the maximum levels established by European Regulations for lettuce.