Postharvest quality and metabolism changes of daylily flower buds treated with hydrogen sulfide during storage

Daylily flower buds are a good source of nutrients and contain lots of bioactive compounds, but they are subject to deterioration after harvest, which limits the taste and consumer satisfaction. Hydrogen sulfide (H2S) has been regarded as an important gaseous signaling molecule, which could prolong postharvest freshness of fruits and vegetables. The present study aims to investigate the effects of H2S on postharvest quality and metabolism changes of daylily flower buds during storage. The results showed that 3.2 mM NaHS (H2S donor) effectively inhibited weight loss, blooming and decay of daylily during storage. H2S application markedly reduced the accumulation of malondialdehyde and H2O2. H2S treatment also delayed the loss of total protein and antioxidant glutathione, and maintained the activities of antioxidant enzymes superoxide dismutase and catalase at higher level compared to control group. Widely targeted metabolomics identified various differentially accumulated metabolites (DAMs) during storage and with H2S treatment of daylily. These DAMs largely distributed in the classes of amino acids, organic acids, sugars and alcohols, terpenoids. A special focus was given to 303 common DAMs between the comparison of CK0 vs. CK6 and CK6 vs. T6, of which the DAMs were mainly enriched in the KEGG pathways of monobactam biosynthesis, pyrimidine metabolism, glycine, serine and threonine metabolism, arginine biosynthesis, pentose and glucuronate interconversions. Four DAMs including Cytidine 5′-Monophosphate, Fumaric Acid, Hydroxypyruvic Acid, 2′-Deoxycytidine-5′-Monophosphoric Acid exhibited great downregulation during storage, and H2S treatment dramatically recovered their relative contents. This study indicated that H2S treatment offers the potential to preserve the quality of daylily flower buds and extend their postharvest life.