Hydroponic production of purslane as a sodium-removing vegetable in NaCl-rich nutrient solution

Abstract

To evaluate the potential of producing purslane (Portulaca oleracea L.) as a sodium (Na)-removing vegetable hydroponically at moderate NaCl salinity, two cultivars (Green and Golden) were grown in solutions with added 0, 6, 8, and 10 mM NaCl (the actual Na+ concentrations ≈2, 8, 10, and 12 mM, respectively). At harvest, 26 days after transplanting, apparent growth and biomass accumulation were not negatively affected by 6 to 10 mM added NaCl compared with 0 mM added NaCl. However, with the increase of added NaCl concentration from 0 to 6 to 10 mM, the sodium removal showed a 1- to 3-fold increase up to 0.26 to 0.41 mmol/plant, and 225.7 to 300.2 mmol·kg-1 dry weight (DW) or 0.90 to 1.32 mmol·L-1 H2O, respectively. 'Green' produced greater biomass and removed more sodium per plant than 'Golden'. 'Golden' had more of a dwarfed and compact canopy than 'Green'. Sodium removal rate (mmol/plant/day) was the highest during the first 7 days after transplanting, but the fresh weight increase rate (g/plant/day) increased gradually as growth progressed. Results suggest that it is possible to hydroponically produce purslane in nutrient solutions with 8 to 12 mM Na+. Despite the high sodium-removal capability, purslane cannot be used to reduce Na+ concentrations in NaCl-rich hydroponic solutions. The biomass yield and the sodium removal of individual plants were affected by different cultivars and time after transplanting.