NaCl stress enhances silicon tissue enrichment of hydroponic "baby leaf" chicory under biofortification process

The effects of saline stress on the silicon (Si) tissue enrichment (Si biofortification) of ready-to-eat "baby leaf" chicory in hydroponic floating system were studied. Four combinations of Si and NaCl levels in the nutrient solution were compared: i) 0 mM Si - 0 mM NaCl ('Control'); ii) 3.6 Si - 0 NaCl ('Si'); iii) 0 Si - 50 NaCl ('NaCl'); and iv) 3.6 Si - 50 NaCl ('Si + NaCl'). Si in combination with salt stress enhanced the Si tissue enrichment with respect to biofortification under control conditions [11.4 vs 3.06 mg 100 g-1 fresh weight (FW), respectively]. However, Si was not able to restore growth of plants under salinity compared to normal conditions. Bioaccessible Si in chicory under 'Si + NaCl' treatment was the highest in the experiment (3.73 mg 100 g-1 FW). The nitrate content was not influenced by salinity neither by Si, while the oxalate content was extremely low in all treatments, thus not compromising the enhanced nutritional value of the biofortified chicory. Application of salt stress could be considered an effective strategy to enhance the silicon tissue enrichment of hydroponic chicory under biofortification process.