Cytological Evidence for the Pathway of Synthesis, Accumulation, and Secretion of Rose Essential Oil

Abstract

Rosa rugosa Thunb. is an important ornamental and economic plant. Essential oil extracted from its flowers is known as “liquid gold” and has a high economic and health value. In this study, the developmental process of secretory epidermal cells of petals, the location of essential oil synthesis and accumulation, and the associated secretory pathway were studied by using Chinese R. rugosa as a test material. Results showed that rose essential oil might be synthesized in two pathways: direct synthesis in plastids and conversion from starch grains. Although starch grains acted as a precursor for essential oil synthesis and provided energy during the synthesis process, the endoplasmic reticulum initially processed a portion of osmiophilic oil for transport and reprocessing through the vesicles of the golgi apparatus. The energy for this process originated from the mitochondria, and the oils were stored in central large vacuoles. Essential oils passed through the cytoplasmic membrane in two ways: through breaks of the cytoplasmic membrane and through exocytosis. This study laid a cytological foundation for regulating the synthesis and metabolism of rose essential oil and provided an important reference for cytologically studying volatile oils in other plants.