Determination of volatile oil and non-volatile organic compounds contents and ultrastructure changes in the petals of Dendrobium huoshanense upon Zn application

The petals of Dendrobium huoshanense have great potential as functional food because of their pleasant fragrance and health values. To obtain high-quality raw materials for functional food production, more attention is being directed toward improving the food quality traits of D. huoshanense petals under field cultivation conditions. In this study, we investigated the effects of Zn application on the volatile oil and non-volatile organic compounds contents in the petals of D. huoshanense. Furthermore, the mechanism was also studied from the perspective of petal ultrastructural changes. Volatile oil constituents were investigated using gas chromatography-mass spectrometry. The contents of non-volatile organic compounds, including soluble sugar, free amino acids, and phenolic compounds, were investigated using chemical analysis methods. Ultrastructural changes were observed via transmission electron microscopy. The results showed that Zn application increased the yield of volatile oils (primarily terpenes and their derivatives) and non-volatile organic compounds from the petals of D. huoshanense. Different levels of Zn treatments changed the production of the above-mentioned volatiles and non-volatile compounds to varying degrees. The maximum rate of increase in the content of volatile oil, soluble sugars, free amino acids, and phenolic compounds was 28.57%, 33.53%, 28.89%, and 58.41%, respectively. Ultrastructural changes at the cellular level showed that Zn application promoted vacuole fusion and increased the production of mitochondria, starch grains, and lipid droplets. In conclusion, Zn application improves the production of volatile oils and non-volatile organic compounds. Ultrastructural analysis has provided new anatomical insights into the production of volatile oils and non-volatile organic compounds.