Detailed explanation of flower preservation methods to extend the ornamental period of fresh flowers
Flowers, especially cut flowers, are often treated with flower preservatives after harvest to maintain the best quality, delay aging, and resist changes in the external environment. Flower preservatives include general preservative solutions, hydration solutions, pulse solutions, STS pulse solutions, bud-opening solutions, and vase-holding solutions. At every stage of harvest and handling, from cultivation to wholesale, retail, and consumption, flower preservatives can be used. After preservation treatment, many cut flowers can have their lifespan extended by 2 to 3 times. Flower preservatives can make flowers larger and maintain the color of leaves and petals, thereby improving flower quality.
Most commercial preservatives contain carbohydrates, fungicides, ethylene inhibitors, growth regulators, and mineral nutrients. Their functions are reviewed separately below.
Carbohydrates: They are the main nutrient source and energy source for cut flowers, and they can maintain all physiological and biochemical processes of cut flowers after separation from the mother plant. Externally supplied sugar sources will participate in extending vase life and play a role in maintaining the structure and function of mitochondria in cut flower cells. By regulating transpiration and cell osmosis, they promote water balance and increase water absorption. Sucrose is one of the most widely used carbohydrates in preservatives, and fructose and glucose are sometimes also used.
Different cut flower species or different varieties of the same species have different suitable sugar concentrations in preservatives. For example, in bud-opening solutions, the optimal concentration for carnation is 10%, while chrysanthemum leaves are sensitive to sugar and generally use 2%, and rose is prone to leaf burn when higher than 1.5%. The optimal sugar concentration is also related to the treatment method and duration. Generally speaking, for a specific cut flower, the longer the preservative treatment time, the lower the required sugar concentration. Therefore, pulse solutions (treated for a shorter time after harvest) have a high sugar concentration, bud-opening solutions have a medium concentration, and vase-holding solutions have a lower sugar concentration.
Fungicides: The microorganisms growing in vases include bacteria, yeasts, and molds. After these microorganisms multiply in large numbers, they block the flower stem vessels, affect water uptake by cut flowers, and produce ethylene and other toxic substances that accelerate cut flower aging. To control microbial growth, fungicides can be added to preservatives or mixed with other ingredients.
Ethylene inhibitors: Silver thiosulfate (STS) is currently the most widely used and best ethylene inhibitor in the floral industry. It has good mobility in plants and has a highly efficient inhibitory effect on ethylene synthesis in flowers. It effectively extends the vase life of many flowers. STS must be prepared just before use, and the prepared solution is best used immediately. If it is not used immediately, it should be stored away from light. It can be stored in a dark environment at 20-30°C for 4 days.
Growth regulators: Growth regulators are used in flower preservatives, including synthetic auxins and plant endogenous hormones. Plant growth regulators can be used alone or mixed with other ingredients. They can induce or inhibit various physiological and biochemical processes in plants, thereby delaying the aging process of cut flowers. Among them, cytokinins are the most commonly used. They mainly inhibit ethylene production. When applied, they can be sprayed or dipped. The optimal concentration is 10-100 ppm, and dipping for 2 minutes is sufficient. If the time is too long, adverse consequences may also occur. Carnation has the best response to this treatment.
The above are the components of flower preservatives, but in actual production, the main components of flower preservation are sugar and fungicides, and sometimes 1-2 additional components are added. Because some cut flowers secrete harmful substances from the stem ends and leaves submerged in water, which can harm themselves and other flowers in the same vase, the vase should be changed with fresh preservative at regular intervals.