عنوان مقاله [English]
Introduction: Narcissus is a genus of hardy, spring-blooming, bulbous plants in the family Amaryllidaceae. Numerous studies have demonstrated positive effects of various chemical additives (e.g. biocides, surfactants, ethylene inhibitors, wound healing enzyme inhibitors) on the postharvest, water relations and longevity of cut flowers. Cut flowers can have limited commercial value because of their dehydrating during vase life that decreased water uptake. Petal senescence is part of a developmental continuum in cut flowers and proceeded by tissue differentiation, growth and development of seeds and coordinated by plant hormones. Senescence can be studied at cellular, tissue, organ or organization level as a genetically programmed event. The vase life of cut narcissus flowers is often very short. The development of senescence symptoms is caused by vascular occlusion, which inhibits water supply to the flowers. Petal senescence was marked by the loss of turgor in petal tissue followed by complete wilting. The development of occlusions is thought to be caused by various factors, such as bacteria, air emboli and physiological responses of stems to cutting. However, despite anecdotal evidence of positive effects, improving postharvest water relations of cut flowers by various physical stem-end treatments is little researched.
Materials and Methods: The Narcissus flowers harvested from Khafr city of Fars province, in February 2015. The Thyme plants harvested in September 2014 and Savory plants harvested in December 2014 and then submitted to hydrodistillation in a Clevenger-type apparatus for 3 hours. This study was carried out in a completely randomized design with 3 replications. The treatments included control (distilled water), two levels of Savory essential oil (50 and 100 ppm) and two levels of Thyme essential oil (100 and 200 ppm). 2% sucrose were added to control and other of treatments . The cut flowers were also kept at temperature of 20±2 ºC with air humidity (RH) of 70±5%. Different parameters including flower weight, uptake of preservative solution, and wilting of flowers were measured every 2 days (0, 2, 4, 6 and 8) and antioxidant enzyme activity (APX) were measured in days of 0, 4 and 8 during storage period, and at the end of experiment, the vase life were measured. The results analyzed by SAS software and drawing tables and diagrams done by Excel software.
Results and Discussion: The results showed that Savory essential oil 50 ppm treatment was effective in improving the flower weight of cut narcissus by increasing uptake of preservative solution and also reducing wilting of flowers and antioxidant enzyme activities. At 200 ppm of thyme essential oil observed reductionin flower weight and uptake of preservative solution, but increasing in wilting of flowers and antioxidant enzyme activities. At 50 ppm of savory essential oil with average days 12.26, the vase life of cut flowers increased significantly as compared to control (10.36) and at 200 ppm of thyme essential oil treatment with average days 8.53, observed decrease invase life of cut flowers compared to control. Impaired water uptake is typically caused by cut stem occlusions due to microbial, physiological and physical plugging of xylem vessels. Essential oils constituents and derivatives have a long history of application as antimicrobial agents in areas of food preservation and medicinal antimicrobial production. physical treatments damage xylem vessels, allow increase of microbes and increase nutrient supply for microbes, which occlude stems. Recently many works carried out about application essential oils as antimicrobial agents under in vitro and in vivo condition and indicated that essential oils could increase postharvest quality of many horticultural crops such as tomato, table grape and kiwifruit (1, 15 and 24). In addition to improving water uptake, other approaches to maintaining a positive postharvest water balance for cut flowers and foliage include minimizing water loss though reduction in leaf area, keeping them in an environment conducive to less water loss (viz. low temperature and high RH) and providing compatible osmotica (e.g. sucrose) in vase and/or pulsing solutions. The loss of membrane integrity has been shown to cause an increase in the permeability and leakage during senescence in various flowers.
Conclusions: Results of this study showed that savory essential oil treatments increased quality and vase life of narssisus cut flowers compared to control At higher concentrations of thyme (200 ppm) the flowers remained closed, wilted quickly and senesced before controls.