Floral preservatives are widely recommended for cut stems and are extensively used in floral arrangements by wholesalers, retailers, and consumers for extending longevity and maintaining quality (Ahmad et al., 2013b; Çelikel and Reid, 2002; Nowak and Rudnicki, 1990). They maintain water uptake by acidifying solutions and controlling microbial growth (McDaniel, 1996) and provide carbohydrates necessary to carry on metabolic activities after harvest (Meyer, 2010). They can improve color development of petals, encourage flower opening, and increase flower head size (Nowak and Rudnicki, 1990).
Several manufacturing companies produce different types and brands of floral preservatives, including hydrators and holding or vase solutions. Hydrators are used immediately after harvest or dry storage to improve water uptake by the stems as these contain acidifying agent without sugars. Holding/vase solutions contain sugars along with acidifiers and biocides, which provide food for maintaining metabolic processes and continued flower opening during vase life.
Among acidifiers, citric acid is the most common compound and is used to lower the pH of the preservative solutions and control microbial proliferation. Citric acid has been found effective for cut roses [Rosa ×hybrida (Jowkar et al., 2012)], gladiolus [Gladiolus hybrids (Tiwari et al., 2010)], carnations [Dianthus caryophyllus (Kazemi et al., 2012)], tuberoses [Polianthes tuberosa (Jowkar and Salehi, 2006)], and lisianthus (Kiamohammadi and Hashemaabadi, 2011). Citric acid lowers the pH of cell sap and prevents the blockage of xylem vessels, thereby improving water uptake and extending longevity. It promotes floral opening and maintains postharvest quality of cut tuberose spikes (Jowkar and Salehi, 2006).
Another compound used extensively to lower solution pH and control detrimental microbes in preservative solutions is aluminum sulfate. It is extensively used as a biocide for cut roses (De Stigter, 1981), lisianthus (Liao et al., 2001), and many other cut flower species. It has also been reported to improve keeping quality and vase life of cut roses (Ichimura et al., 2006) by stabilizing petal anthocyanin contents and lowering pH.
Sugars are the integral component of flower foods, providing essential carbohydrates to the cut stems and continuing metabolic processes necessary for extension of vase life. However, sugars must be used along with antimicrobial compounds to prevent microbial buildup in the solutions (van Doorn, 1997). Among these biocides, silver compounds such as silver nitrate and silver thiosulfate, chlorine compounds such as sodium hypochlorite and sodium dichloroisocyanurate, and several other compounds such as cobalt chloride, 8-hydroxyquinoline citrate or sulfate, quaternary ammonium chloride, or isothiazolinone are used to prevent microbial proliferation in vase solutions. Because of environmental hazards associated with silver compounds and 8-hydroxyquinoline citrate or sulfate and only short-term effectiveness of chlorine compounds, quaternary ammonium chloride and isothiazolinone can be used for handling cut flowers. Quaternary ammonium chloride disinfectant is stable, safe, and effective in controlling germs in vase solutions, particularly when freshly prepared solution is used. Isothiazolinone is another safe, effective, broad-spectrum, and globally approved preservative compound, which can also be used as a biocide in floral preservative solutions (Ichimura et al., 2006). However, limited information is available on effectiveness of these compounds for cut flower longevity.
Several other compounds have been used by the industry as biocides, acidifiers, or both in various homemade floral preservatives. Some of these include lemon/lime soda, lemon juice, vinegar, household bleach, aspirin tablets (Greer and Einert, 1994), pennies, or essential oils of several plant species (Fariman and Tehranifar, 2011; Samiee et al., 2013). However, limited information is available on their effectiveness on cut flowers postharvest longevity and quality. Commercial preservatives are well researched and effective, but not readily available in many parts of the world. In addition, several folk recipes also are being used by the industry and consumers, but limited scientific information is available about their effects on the longevity and quality of cut stems. Therefore, the present studies were conducted to determine the effect of different homemade floral preservatives on four popular specialty cut species. The specific objectives of the studies were to 1) develop readily available, environmentally safe, and low-cost floral preservative(s) for growers, florists, and consumers; and 2) evaluate the effects of different ingredients of folk floral recipes being used by the industry. It was hypothesized that the recipes would extend the vase life of tested species as much as commercial preservative solutions.
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