Document Type : Research Article
Authors
Ferdowsi University of Mashhad
Abstract
Introduction: Gerbera (Gerbera jamesonii Bolus, Asteraceae) commonly known as Transvaal Daisy, is one of the ten most popular and important commercial cut flowers. Gerbera is a perennial, tropical, herbaceous plant with colorful and attractive flowers that are widely used as a decorative garden plant or cut flowers. The most important problem of the gerbera cut flowers is short vase life. The end of vase life of cut gerbera flowers is often due to bending of the scape. The aim of this study was to screen the effects of nanosilver and salicylic acid as pulse treatment and sucrose and thyme, clove and peppermint essential oils as permanent treatment on vase life and some physiological and biochemical traits of gerbera ‘Rosalin’ cut flowers.
Materials and Methods: This study was conducted as a factorial experiment based on completely randomized design with three replications. The first factor was pulse treatments using nanosilver (NS) 5 and 10 mg/L (Nanocid Company, Iran), salicylic acid (SA) 50 and 100 mg/L (Merck Company) and distilled water as control, and the second factor was permanent treatments applying distilled water, sucrose 4% (Merck Company), peppermint (100 mg/L), thyme (100 mg/L) and clove (300 mg/L) essential oils (EO) (Zardband Company, Iran). Pulse treatments were applied for 24 h. Treated stems were then stood into vases containing permanent treatments. Vase solutions were freshly prepared at the beginning of the experiment and not renewed during of the study. The measured traits were: flower vase life, flower water content (WC), relative fresh weight (RFW), water loss (WL), water uptake (WU), total soluble solid (TSS), superoxide dismutase (SOD) enzyme activity and malondialdehyde (MDA) amount (Biovision Colorimetric Assay Kit, USA). The experiment was conducted in the laboratory at 20-22°C, 40-50% RH, and 15 µmol/m2s light intensity (cool white florescent tubes) under a daily light period of 12 hours. The obtained data were analyzed using MSTAT-C program and mean comparison was done using LSD range test.
Results and Discussion: The results showed that NS 10 mg/L with thyme EO 100 mg/L (14.25 days) and NS 10 mg/L followed by peppermint EO 100 mg/L (14 days) had the best effect on longevity and maintaining the water content of gerbera cv. ‘Rosalin’ cut flower, compare to other treatments. Flower WC was high (about 90%) except in 4% sucrose permanent treatment flowers which had negative effect and decreased more rapidly during the vase life period. Despite of antimicrobial preservative application, RFW, WU, WL and TSS generally had a decreasing trend during the experiment. However, it was observed that flowers treated by NS 10 mg/L (0.86 g/g) and thyme (0.77 g/g) and peppermint (0.72 g/g) EOs had the most RFW on the eighth day of experiment, but 4% sucrose (0.59 g/g) permanent treatment reduced RFW during cut flower vase life. The highest WU was respectively observed in SA 100 mg/L (67.28 g), NS 5 (61.31 g) and 10 mg/L (60.35 g) on the second day. According to the results of this research, pulsing by NS 5 and 10 mg/L and SA 100 mg/L resulted in the the most WL on day two (64.24, 57.85 and 64.95 g respectively). TSS of the cut flowers decreased with time, however reduction rates were delayed in SA and NS treated flowers. On the eighth day of experiment, long-term treatment showed the most effect on TSS amount. Flowers treated by NS 10 mg/L followed by 4% sucrose and peppermint EO treatment had the highest TSS amount, respectively 3.50 and 3.17 Bx. As the time passed, the activities of SOD enzyme increased, however, treated flowers showed significantly higher SOD activity compared to the control. Especially NS 10 mg/L pulse treatment, followed by thyme and peppermint EOs, indicated by the highest amounts (241.43% and 233.94%) of SOD activity on seveth day of the experiment. During the experiment, MDA increased in the flowers, so that the highest amount of MDA was detected in control (67.30%) on the seventh day and the lowest was produced in NS 10 mg/L treated flowers followed by thyme (14.88%) and peppermint (19.44%) EOs. Due to the fact that these treatments had the best effects on flower vase life, these results are logical.
Conclusions: Based on the results of this study, new antimicrobial agents such as NS, thyme and peppermint EOs had a positive effect on flower vase life, WC, RFW and WU and reduced the rate of WL and TSS reduction in flowers. It might be due to this fact that these are very effective antimicrobial agents, inhibited the microbial growth and prevented bacterial plugging in conducting tissues. NS particles enter to cell, tissue and organs, so they can inhibit the respiration and electron transfer system and material transfer in microbial cell membrane. The application of natural phenolic compound like EOs reduced the accumulation of MDA and enhanced SOD enzyme activity. Therefore, due to the undesirable results of chemical preservative on human and environmental health, EOs can be very good substitutes for preserving cut flowers postharvest life.
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