Effect of Glucose, Fructose, and Sucrose on Vase Life, Antioxidants Enzymes, and Some Physiologic Parameters of Carnation cv. ‘Yellow Candy’ Cut Flower

Introduction  Carnation (Dianthus caryphyllus L.), from Caryophyllaceae family, is one of the most important cut flowers in the world that its short vase life reduces the economic value. Postharvest longevity of cut flowers can be prolonged using carbohydrates (sugars) in a vase jar. Cut flowers undergo some physiological and biochemical changes that often lead to an early senescence. To delay the aging process in cut flowers, it is necessary to evaluate many aspects of preparation for storage conditions, especially preservative solutions that affect the quality and longevity of these flowers. Many flowers are harvested before they are fully developed, to ensure a long postharvest life and to minimize mechanical damages that might occur during handling. The growth and development of flower buds on cut flowers require food (especially carbohydrates), which is stored in the leaves and stems. These stored carbohydrates can be mobilized for the flower bud to use but maybe they are insufficient when the buds are harvested at a tight-bud stage. To maintain metabolic activities, including respiration, even for cut flowers that have reached full development, it is necessary to provide adequate reserves to achieve acceptable postharvest life. When stored materials are low, leaves and flowers age faster and the petals fade. Under these conditions, supplements can be provided to the flowers by adding sugars such as glucose, fructose and sucrose to the vase solutions. However, it is important to note that a sugar solution is also suitable for the growth of microorganisms, so that an antimicrobial agent should be added to the vase solution as well. Many researches were carried out on prolonging the vase life of cut carnation flowers with different preservative solutions together with an antimicrobial agent. Studies on postharvest longevity of cut carnation flowers using sugars as preservative solutions is low. Therefore, the aim of the present study was to evaluate the effect of sugars (glucose, fructose and sucrose) and application time on vase life and some physiological parameters of carnation cv. ‘Yellow Candy’ cut flowers. Materials and Methods  A factorial experiment based on completely randomized design in three replicates was performed in order to investigate the effect of different levels (0, 50 and 100 g/L) of three types of sugars (glucose, fructose, and sucrose) and two sugar application times (the first and second 24 h, on 2019) on vase life of carnation cv. ‘Yellow Candy’ cut flowers. Some other traits such as water uptake, dry mater, relative fresh weight, protein and carotenoid of petal, leaf chlorophyll, POD and SOD enzymes activity and MDA were also measured. The statistical analysis of data was performed using Statistical Package for Social Sciences (SPSS) v 16.0. Least significant difference (LSD) test at P < 0.05 was used to find out the significance of differences among the mean values.     Results and Discussion Results showed that the effect of different levels of sugars on all evaluated traits was significant. Each three levels of sugars at each two applied times caused to increase vase life and relative traits. Maximum vase life (18 days) was obtained in 50 g/L glucose at the first 24 h with no statistically significant differences with the 100 g/L sucrose and fructose at the first 24 h. The highest water uptakes and dry matter, the lowest POD and SOD activity and minimum MDA were obtained in treatment of 50 g/L glucose at the first 24 h. The study found that the highest levels of petal protein content, chlorophyll a, b, and total chlorophyll were achieved in carnation "Yellow Candy" cut flowers treated with 50 g/L glucose after 24 hours of harvesting. The application of sugars at the first 24 hours after harvesting had a greater impact on improving the vase life of the flowers compared to the second 24 hours. Therefore, the use of glucose as an external holding solution, preferably within the early hours of harvesting, is recommended to prolong the postharvest life of carnation "Yellow Candy" cut flowers. The study also revealed that the use of external holding solutions, particularly sugars combined with antimicrobial agents, can have a positive effect on prolonging the vase life of cut flowers. The concentration of sugar required in the holding solution varies depending on the type of flower being treated, with most flowers requiring a concentration of 2% sugar. However, some flowers may require higher concentrations, up to 4-6%, while others may be damaged if treated with concentrations higher than 1%. The application of sucrose has been shown to increase glucose and fructose levels in petals, further supporting the use of external holding solutions containing sugars for extending the vase life of cut flowers. Therefore, it is important to examine each flower before treating it to determine the optimal concentration of sugars. Sugars are a source of energy and carbon for cut flowers and play an important role in decreasing the protein degradation and ethylene production, maintenance of osmotic balance, increasing water uptake, and finally delaying in senescence process