The secretion pattern of calycine nectar and its removal methods from cut peony flower

Peony fresh cut flowers contain calycine nectar, the secretion of which varies depending on the variety, and the calycine nectar also have adverse effects on the cut flowers during storage or transportation, such as molding, which affects the quality of the cut flowers. In the current study, we investigated the secretion patterns of calycine nectar at different times of the day. The results showed that calyx honeydew accumulation peaked from 00:00–06:00 am. Microscopic observations revealed that the main secretion sites of peony calycine nectar are concentrated on the margins of the sepals and bracts. By analyzing the calycine nectar with non-target metabolome, 1989 metabolites were found and distributed across 22 major chemical classes. Carbohydrate metabolites were detected in sepal nectar using HPLC and enzyme-linked immunosorbent assay, among which sucrose was the most abundant. Through fungal isolation assays, Botrytis cinerea is the main pathogen causing calyx mold, to inhibit the growth of mold on calycine nectar, we used clean water and wash reagent to wash the calyx part of cut flowers, and then stored them at low temperature, the wash reagent had better fresh mass maintenance and were less mold infection and decay rate. In conclusion, calycine nectar secretion exhibits rhythmicity and secretion quantity varies among cultivars, the nectar on the calyx is dominated by sucrose, and B. cinerea is the primary pathogenic fungus infecting the calyx. Exogenous cleaning method application can be considered as a safe and promising procedure to maintain the quality of cut peony during storage period.