The effect of root-applied glycinebetaine and nutrient cutoff on the sweetness, bitterness, and nutrient content of hydroponically grown lettuce during storage.

Root-applied glycinebetaine (GB) is a novel method to enhance the edible quality of hydroponically grown lettuce. However, the effect of root-applied GB on lettuce postharvest quality is unknown. Here we compare the effect of root-applied GB and nutrient cutoff treatment on postharvest quality of lettuce. In nutrient cutoff treatments, the fertigation solution was replaced with tap water with or without GB. Hyperspectral imaging technique was used to investigate the visual quality. The contents of sugars, sesquiterpene lactones, nitrate, minerals, vitamin C, and GB were analyzed. Plants treated with root-applied GB or nutrient cutoff treatment showed higher content of sugars and lower content of nitrate during storage compared to plants treated with fertigation alone. No significant changes in visual quality were observed. GB persisted in lettuce leaves over 13 days. In conclusion, root-applied GB as well as nutrient cutoff treatment coincided with improved quality attributes relevant to consumer and lettuce shelf life.