POSTHARVEST LONGEVITY AND QUALITY OF CUT CARNATIONS, 'PAX' AND 'TABOR', AS AFFECTED BY SILVER NANOPARTICLES

Carnation (Dianthus caryophyllus L.) is one of the most important cut flowers around the world. In cut-flower production, improvement of postharvest longevity and quality besides minimizing wastes are considered as strategic objectives. These kinds of flowers are sensitive to microbial contamination in vase solution, which led to shortened vase life as a result of blocking stem vessels on the cut surfaces. Silver nanoparticles (SNP) are novel antimicrobial agents in extending postharvest longevity of cut flowers. Antimicrobial effects of SNP are due to structural changes in bacterial cell membrane and finally cell death. In this experiment, the effects of four concentrations of SNP including 0 (control), 5, 10 and 20 μl L beside silver nitrate at 100 μl L, all with 4% sucrose in continuous solution were evaluated on extending postharvest longevity and quality of two cut carnations, ‘Pax’ and ‘Tabor’. Electrolyte leakage (EL), chlorophyll (Chl) content, turbidity solution, relative fresh weight (RFW) and solution uptake were also the other traits assessed during this experiment. The results showed the use of continuous solution containing 5 μl L SNP could increase the vase life of cut carnations up to 8.7 and 5.8 days in ‘Pax’ and ‘Tabor’ cultivars, respectively. Also indicated that the concentration of 5 μl L SNP was not only effective in extending the longevity of the cut carnations but also preserving the quality of the flowers as well. INTRODUCTION Carnation (Dianthus caryophyllus) is one of the most important cut flowers around the world. The genus Dianthus belonging to the Caryophyllaceae family and carnation is applied as its common name (Galbally and Galbally, 1997; Jurgens et al., 2003). The main problem of using cut flowers as decorative purposes is their short vase life, senescence and welter of petal. In most cultivars of carnations, progress of senescence is accompanied by a significant increase in the synthesis of ethylene and a consequent climacteric augmentation in respiration ratio (Serek et al., 2006). Vase solution affects quality of flowers by extending vase life as well as preservation of leaf freshness and color of flower organs. The main advantage of vase solution could be related to alleviation of bacterial accumulation at the stem base. Application of silver nitrate and/or silver thiosulfate (STS) on cut-carnations prevented the climacteric increase in ethylene biosynthesis and delayed senescence of the flowers (Nair et al., 2003; Meman and Dabhi, 2006). Nowadays, using silver nitrate is commercially restricted due to its harmful effects on the environment and human health (Damunupola and Joyce, 2006). Silver nanoparticles (SNP) with antimicrobial properties could be a suitable agent for reducing bacterial population in vase solution and improve postharvest quality of cut flowers. Antimicrobial activity of SNP could be related to its lethal effect on bacterial cell membrane causing cell death (Morones et al., 2005). Using nano-silver compounds (NS) in vase solution of cut flowers is a relatively new subject as an antibacterial agent (Solgi