Document Type : Research Article
Authors
Department of Horticultural Science, Ra.C., Islamic Azad University, Rasht, Iran
Abstract
Introduction
Cut tuberose flowers face challenges such as reduced vase life and postharvest quality deterioration. This problem is mainly caused by various factors such as dehydration, vascular blockage due to bacterial growth, ethylene accumulation and oxidative stress, which lead to a reduction in the postharvest lifespan of flowers. To address these challenges, the use of chemical and natural compounds has been considered an effective method to extend postharvest longevity and maintain the quality of cut flowers. Aluminum sulfate helps to preserve the freshness of cut flowers by reducing microbial growth, improving water uptake and preventing vascular blockage. The use of aluminum sulfate in vase solutions has shown to increase of the postharvest lifespan in certain cut flowers, such as roses, gardenias and lisianthus. Plant essential oils (containing phenol), possess antioxidant, antibacterial and antifungal properties. They can inhibit microbial growth in vase solutions and prevent cellular damage caused by reactive oxygen species (ROS) or free radicals. The positive effects of certain essential oils on extending the vase life of some cut flowers, including gerberas, roses and alstroemerias, have been reported. Cobalt chloride prevents vascular blockage caused by bacterial agents in stems and maintains a high-water flow rate, leading to improved water uptake by cut flowers. This salt can also extend vase life by inhibiting ethylene production, preventing its accumulation and reducing respiration. The beneficial effect of cobalt chloride on increasing the vase life of some ornamental cut flowers, including roses, carnations, tuberoses, gladiolus and chrysanthemums, has been reported. 8-Hydroxyquinoline sulfate (8-HQS) is an inhibitor of ethylene production and reduces respiration rate. In cut flowers such as dendrobium, gerbera and gladiolus, 8-HQS extended the vase life by preventing microbial growth, reducing respiration rate and enhancing water absorption. This study aimed to investigate the effects of aluminum sulfate, Eryngium spp. essential oil, cobalt chloride and 8-HQS on the postharvest longevity of cut tuberose flowers (Polianthes tuberosa).
Materials and Methods
Cut tuberose (Polianthes tuberosa) flowers were obtained from a commercial producer in Tehran Province. To standardize the stem length, all flowers were recut at a 60 cm distance under water and immediately transported to the postharvest laboratory at the Faculty of Agriculture, Islamic Azad University, Rasht Branch, to prevent dehydration. Upon arrival, the flowers were placed in distilled water to maintain hydration. For the experiment, five cut flowers were placed in each 2-liter plastic vase and then treated with specific concentrations of the experimental factors. The study was conducted based on a completely randomized block design with three replications. The effects of different concentrations of aluminum sulfate (50, 100 and 150 mg.L-1), Eryngium essential oil (10, 20 and 40%), cobalt chloride (200, 300 and 400 mg.L-1) and 8-HQS (100, 200 and 400 mg.L-1) on cut flowers parameters such as vase life, water uptake, fresh weight loss, chlorophyll content, malondialdehyde (MDA) as an indicator of lipid peroxidation, bacterial colony count and antioxidant enzyme activity were evaluated. Thus, the present experiment consisted of 12 treatments, 3 replications and 5 flower stems per replication, totaling 36 experimental units (plots). Treatments were applied permanently, with each treatment prepared based on a 500 mL volume in the plastic vase. Data were subjected to analysis of variance (ANOVA) and means were compared by the LSD at P < 0.05 using the SAS ver. 9.2 software.
Results and Discussion
The results showed that treatment with aluminum sulfate significantly increased vase life and prevented fresh weight loss. Aluminum sulfate improved water uptake and preserved chlorophyll content, thereby enhancing the longevity of the flowers. Eryngium essential oil also had a positive effect on maintaining flower quality due to its antimicrobial and antioxidant properties. Results of the variance analysis showed that treatments with aluminum sulfate, Eryngium essential oil, cobalt chloride and 8-HQS significantly increased the vase life of tuberose cut flowers (P < 0.01). The effect of treatments was significant for most traits. The longest vase life (12 and 11.50 days) was observed in aluminum sulfate at 100 and 50 mg.L-1, respectively, while the control treatment had a vase life of only 8 days. The highest water uptake was observed in treatments with aluminum sulfate (100 mg.L-1), 8-HQS (200 mg.L-1) and Eryngium essential oil (10 mg.L-1). The control treatment had the highest bacterial population at the stem base (33 CFU.mL-1) and vase solution (73 CFU.mL-1). 8-HQS (400 mg.L-1) showed the lowest bacterial population at the stem base (4 CFU.mL-1). Just some treatments were selected for measurement of enzymes activity. Among the selected treatments, Eryngium essential oil (20 mg.L-1) exhibited the highest peroxidase (POD) enzyme activity, while the control treatment (0.07 µmol.g-1 fresh weight) had the lowest. The control treatment (9.47 µmol.g-1 fresh weight/min) showed the highest catalase (CAT) enzyme activity, while cobalt chloride (300 mg.L-1, 1.84 µmol/g fresh weight.min-1) had the lowest. Aluminum sulfate can partially reduce ethylene production and respiration rate in cut flowers. It primarily acts as an antimicrobial agent, indirectly extending vase life. Some studies suggest aluminum may moderately reduce lipid peroxidation in cell membranes. The aluminum ion may interact with cell walls, enhancing tissue rigidity and delaying wilting. Studies on roses, peonies and gladiolus confirmed that aluminum sulfate delays senescence by inhibiting microbial growth, preventing bacterial blockage and improving water uptake. Plant essential oils (e.g., in tuberose, chrysanthemum, gerbera, gladiolus and carnation) extend postharvest life due to their antimicrobial and antioxidant properties, reducing microbial load in vase solutions and ethylene production. 8-HQS, as a disinfectant, extended vase life in peonies, dendrobium and gladiolus by inhibiting bacteria, enhancing water uptake, delaying senescence, suppressing ethylene and reducing respiration rate. Increased POD activity in treated flowers indicates enhanced antioxidant defense, crucial for neutralizing free radicals and mitigating oxidative stress. Reduced CAT activity in treated tuberose flowers may result from lower ROS production, direct inhibition of enzyme activity, hormonal/metabolic signaling changes and delayed oxidative stress and senescence.
Conclusion
These findings suggest that the use of these compounds particularly aluminum sulfate at the concentration of 100 and 50 mg.L-1 can be an effective method to improve the postharvest longevity and quality of cut tuberose flowers.
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