CARBOHYDRATE METABOLISM IN INFLORESCENCES OF EPIDENDRUM IBAGUENSE

Abstract

The purpose of this work was to determine changes in the carbohydrate content and sucrolytic activity in flower structures of Epidendrum ibaguense. Inflorescences were harvested at the different stages of development: 0 – mature closed bud, 1 – fully opened flower, 2 – senescence onset (red petals and twisted red labellum), 3 – wilted and senescent flower. Levels of total soluble sugar, reducing and non-reducing sugars and starch, as well as acid and alkaline invertase and sucrose synthase activities were determined. In inflorescences at the stage 3 the consumption of carbohydrates was observed during their postharvest life, as both carbohydrate types decreased along with time. The levels of soluble sugars, non-reducing sugars and starch did not differ over time in the inflorescence at stages 0, 1 and 2. Reducing sugar content decreased in flowers at stages 0, 1 and 3. No significant difference in starch content was detected among stages 0 to 2; starch showed an increase in senescing flowers. Soluble acid invertase was the main enzyme active throughout flower ageing. Sucrose synthase activity was kept low, with a relative increasing during senescence, which coincided with the highest levels of starch. In conclusion, carbohydrate metabolism varied along with the stage of development and the postharvest life of inflorescences of E. ibaguense.