Understanding the physiology of floral maturation in <i>Gardenia jasminoides</i> through metabolomic, histochemical and ultrastructural analyses

BACKGROUND AND AIMS: Understanding floral metabolism is important for studying the physiology of flowers that have direct relevance with the process of maturation and senescence. Gardenia jasminoides, an evergreen Rubiaceous shrub, is widely cultivated worldwide for their fragrant flowers. No detailed investigation has been conducted as a whole to study the floral development and senescence encompassing physiological, histochemical, metabolomic and ultrastructural changes of flowers in general, and G. jasminoides in particular. Such comprehensive insight on floral maturation may help floriculturists in formulating new practices to prolong the vase life of commercially cultivated flowers. METHODS: For this study, temporal investigations of a few physiological attributes, enzymatic antioxidant activities and histochemical properties were made with G. jasminoides flowers. Alterations in metabolomic landscape were studied by in-depth analysis of specialized and central metabolites. Further, activities of selected carbohydrate metabolic enzyme were tested using in vitro and in situ assays. Electron microscopes were utilized to check the extra- and intra-cellular changes during floral maturation. KEY RESULTS: Substantial changes in physiological features were observed when the buds transitioned to flowers, and again during senescence. A prominent role of ROS molecules was observed in flower unfurling and senescence. Flowers of G. jasminoides were shown to emit maximum quantity of scent volatiles during the anthesis stage of maturation. Histochemical and metabolomic studies showed the anthesis stage to be metabolically most active. The buds convert into sinks as the petals unfurl, and the sink strength seemed to get reduced as the flowers enter senescent stage. Visualizing the changes of intracellular landscapes provided a deeper insight into the physiological changes during maturation. CONCLUSION: Different floral maturation stages might be associated with distinct characteristic features, which are underlined by rearrangements in metabolism throughout the maturation stages. A conversion from autotrophic to variable degrees of heterotrophic metabolism was also detected in the flowers throughout their lifespan.