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Post-harvest management of cut flowers

Post by on Monday, September 27, 2021

First slide
Floriculture is an important as well as fast growing branch of horticulture growing around 10-12 percent annually. Among the total floriculture trade which is around $30 billion, cut flower share is around 60 percent.
The day-to-day modern age is enjoying every moment and every memorable day with flowers. Be it an inaugural function or any important day e.g., teacher’s day, Mother’s Day, valentine’s day, friendship day or a national day, all the occasions include a utilization of flowers, particularly cut flowers.
Besides this all the feelings are now expressed with the presentation of flowers. The expression of love is done by presenting rose, expression of women's love by presenting red rose or carnation, similarly iris for message, snapdragon for presumption, daffodil for regard, marigold for sorrow, lotus for purity, and lily for luxury.
This indicates that flowers have a prime position in current day to day life. Keeping in view the importance of cut flowers and its fast-growing rate due to increasing demand it diverts attention towards the various aspects of cut flowers particularly how to extend vase life.
Earlier flowers were judged on the basis of physical parameters like colour, size of bloom, stem length of flower, quality of leaves and overall appearance but, besides these factors longevity after harvest is the most important factor considered.
Post-harvest plays the most important role as the aesthetic value pays the price of the produce. In any marketing system, quality assurance of the product plays the most important role so as to earn profit and this is highly implemented on highly perishables like flowers. Quality of a flower to a consumer is very important as it is associated with the status and dignity of a consumer.
The most important factors associated with the vase life of a cut flower are:
•        Stage of harvest.
•        Pre-cooling.
•        Pulsing.
•        Recutting of stem.
•        Prompt and careful handling.
•        Packaging.
•        Maintenance of ideal storage.
 
 Stage of harvest
Among all the above factors, the optimum stage of harvest plays the most important role as it is directly related with the quality retention and economic returns. Development of a flower and vase life after harvest depends on water balance, carbohydrates and other synthates in plant tissue.
Flowers, if harvested at an immature stage are detrimental for vase life. The development of xylem vessels plays an important role as it is responsible for maintaining water balance, carbohydrate content and related aspects as the flow of solution and its capacity to hydrate and rehydrate depends upon the maturity of xylem vessels. For example, a rose if cut at an immature stage will suffer from a bent neck which is caused by insufficient maturity and hardening of vascular tissues.
In gerbera a lack of cavity for solution uptake is observed if harvested at an immature stage. Besides this cut flowers have a high surface area to volume ratio and are prone to water loss. Vase life of a cut flower largely depends upon the constituent of water when cut and ability of water to rehydrate after continuous shipping.
The other factor is that pulsing will be effective only when xylem will have capacity to take post-harvest solution at optimum level. Thus, the knowledge about the stage of harvest is important, besides this the storage life is improved as the flowers cut at optimum level minimizes the respiratory activities and transpiration losses are minimum.
Apart from this the depletion of stored food material takes place at low rates. The one most important advantage is that bruising losses are minimum and transportation as well as storage becomes easy. However, the flower crops differ in harvesting criteria as some are physiologically fit for harvesting at tight bud stage, some at colour showing stage, some at half open stage and some at full open stage.
 
Pre cooling
It is the most important operation as far as vase life of a cut flower is concerned. The operation aims to remove ground heat as well as prevent the xylem blockage which is due to entry of air in the xylem vessels. Immediately after harvesting the stem of the cut flower is immersed in cold water contained in a container. It removes field heat and minimizes ethylene rise.
The time gap between the harvesting and the pre-cooling should be minimum. If the time gap is more the air may enter the xylem vessel and cause blockage which in turn restricts hydration. If care is not taken no other alternative can save the flower. The temperature of the pre cooling medium should be minimum.  The pre-cooling is mainly done in two ways: room cooling and forced cooling.
 
Under room cooling the flowers are kept in wet or dry conditions at an optimum temperature depending upon the crop.
As far as forced cooling is concerned, the flowers are kept in perforated boxes which are subjected to cool air blasts in an embedment temperature.
The most important consideration for pre-cooling is that the temperature should be kept optimum as per the type of flower as some flowers are tropical in nature, some sub-tropical and some are temperate in habits.
 If the temperature is below or above the optimum it will cause either chilling or heat injury. For example, if anthurium or orchids are cooled below 7 0C it will be a chilling injury and if rose or carnation are cooled at 7 0C it will be a heat injury.
 
Pulsing
Pulsing means to provide nutrients to cut flowers after it is detached from the parent plant from which it was getting nutrients. The nutrition is required for successful bud opening, retention of flower freshness besides minimizing ethylene rise. In other words, it is the application of a holding solution given to a flower under artificial condition so that the physiological and biochemical process will go on under a condition where it is not having natural habitat.
The pulsing solution consists of anti-ethylene compounds, biocidal compounds and sucrose which are a carbohydrate source for flowers. As far as anti-ethylene compounds are concerned, it includes use of gibberellin, auxin, cytokinin or growth retardants. As evident from research GA @ 50-100 ppm is found excellent. As far as auxin is concerned NAA @ 25-100 ppm can be used in pulsing solution. BA has been found enhancing vase life of different flowers when used in vase solution.
The growth retardants are mostly used in pulsing solution for extending vase life of cut flowers as it has a pronounced effect on minimizing the ethylene rise. The example of growth retardant used in pulsing solution are paclobutrazol, cycocel etc. The most important combination of pulsing solution is the biocidal compound.
These are such compounds which minimize the microbial attack to the flower stem and thus prevents the flower from deterioration. Beside these biocidal compounds create acidic conditions by lowering the pH of the solution which in turn helps in effective solution uptake by flower stem.
Apart from this under low pH the microbial population is checked. The most extensively used biocidal compounds are 8HQC, STS, CaCl2, COSO4 etc., but 8HQC STS, CaCl2 are recommended due to excellent effect. The combination of sucrose helps in maintaining the optimum level of carbohydrate which is necessary for successful bud opening as it is a source of energy. So, a pulsing solution must be a combination of all these factors.
 
Re cutting of stem
After the flowers are brought from field or after shipment there are chances that flower stems may face xylem blockage due to entry of air into the vessels and this in turn will not permit solution uptake and the result will be wilting of flowers.
Therefore, a fresh clean cut prevents stem damage and allows effective solution uptake. The procedure of re-cutting involves the removal of 2.5-5 cm stem as this area is more prone to contain microorganisms or bubbles of air that block water transport in cells.
 
 
Re hydration
The ability of a flower to re-hydrate in a specific time period determines its vase life. After transporting flowers lose vigor and water loss may be up to 5-10%. Flowers should be hydrated around 15 -24 hours before transporting and immediately after reaching the destination.
 
 Prompt and careful handling
Flowers should be handled very carefully without bruising damage, environmental damage or the damage of harvesting, transportation etc. The successful production can be said only when it reaches the consumer safely and gets proper economic value.
 
Packaging
Any packaging material should facilitate low respiration rate during transportation and at the same time should not retain the heat produced by commodities. Apart from this, packaging material should have a capability not to allow the external heat to the ambient condition.
Beside this it should have a quality of easy storage, transportation, handling, eco friendly and should provide optimum condition for justification of quality produce through visual way. It should ensure the option of representing trade name, quality and other character of the commodity which is inside.
The most ideal packaging material used in cut flower crops is corrugated cardboards. The size of cardboard varies from one flower crop to another crop. For example, for carnation the ideal size for packaging is the box measuring 122 × 50 × 30 cm which accommodates 800 flowers. For chrysanthemums the size of the box is 91 × 43 × 15 cm. For gerbera the ideal size is 100 × 30 × 10 cm. For roses the size ideal for packaging is 120 × 45 × 25 cm.
 
Storage
The main consideration for storage should be low temperature and high humidity. At low temperature respiration rate is minimum and at high humidity the transpiration losses are minimum.
Most of the cut flower is stored at 0.5 to 2 degrees Celsius with relative humidity of 90 to 95 percent. However, the temperature requirement varies from tropical, sub-tropical and temperate cut flowers. Thermometer should be kept for recording the temperature of the store house.
Transport of flowers should be done in climatic controlled vehicles. Always use clean buckets and utensils for cut flowers so as to avoid infection of microorganisms. Ethylene can be removed from the cold storage by simply ventilating the air not polluted with ethylene. Use of potassium permanganate oxidizes ethylene for ethylene removal.
Fresh flowers should be kept away from fully opened or newly harvested flowers. Remove the dead dying stem and sweep all plant parts of the floor as this releases ethylene which harms the produce.
 

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