Presentation on theme: "Postharvest handling of cut flowers Advanced Course on Postharvest Technology November 2003, Mauritius Dr. Ron Porat Dept. of Postharvest Science of Fresh."— Presentation transcript:
Postharvest handling of cut flowers Advanced Course on Postharvest Technology November 2003, Mauritius Dr. Ron Porat Dept. of Postharvest Science of Fresh Produce ARO, The Volcani Center, Bet Dagan, Israel
Among horticultural crops, cut flowers have perhaps the highest commercial value but are most perishable: they loose a lot of water, have high respiration rates, and are susceptible to physical damage.
Factors affecting postharvest longevity and quality of cut flowers Maturity stage Carbohydrate supply Temperature Water loss Ethylene Mechanical damage Diseases
Maturity stage Cut flowers are usually picked when the buds are starting to open. (rose, gladiolus). In some cases, the flowers must be picked open (chrysantemum, carnation).
Carbohydrate supply The reserves of starch and carbohydrates in the leaves and stems are usually not enough to support energy for proper bud opening and maintenance. Therefore, cut flowers are often pulsed for up to 24 h with a solution containing sugars (from 2 to 20% sucrose). Control5% Sucrose Liatris
Temperature Flowers have high respiration rates, which increases logarithmically with increasing temperatures. Cooling slows respiration and delays senescence. The optimal storage temperatures for most cut flowers are between 0-2ºC. Tropical flowers, like anthurium and several orchids, that are sensitive to low temperatures should be kept at 10-13ºC.
Forced-air cooling of cut flowers
Water loss Flowers have a large surface area and, therefore, they loose water rapidly. Flowers should be stored at low temperatures and at a relative humidity of 95% to reduce water loss and wilting. The main causes for problems in water uptake are: Air embolism: occurs when bubbles of air are drawn into the stems at the time of cutting. Air bubbles can be removed by re-cutting the stem. Bacterial plugging: Growth of fungi and bacteria can plug the water transpiration system. To avoid this, holding solutions should be acidic (pH 3.5) and contain germicides.
Ethylene Many flowers perish rapidly in response to ethylene. Carnations, orchids, etc. – ethylene induces senescence Snapdragon, delphinium, etc. - ethylene induces abscission It is important to avoid pollution with ethylene, to remove ethylene from storage rooms by ventilation, and to treat the flowers with ethylene action inhibitors (STS, 1-MCP).
Mechanical damage Bruising and injuries are undesirable from an aesthetic point of view, but also provide pathogen invasion sites. The cut flowers must be wrapped carefully and be protected by polyethylene sleeves, shredded paper, etc.
Diseases Decay, especially gray mold caused by Botrytis cinerea, provides a major cause for postharvest losses. The cut flowers should be kept at low temperatures without water condensation.
Carmen ControlTOG-MJ-1 A. Red Charm ControlTOG-MJ-1 B. Frisco Control TOG-MJ-1 C. Effect of combined treatment of pulsing and spraying with TOG-MJ-1 on appearance of various cut rose cultivars following artificial infection with Botrytis (Spraying with 0.6% TOG-MJ-1 / pulsing with 0.4% TOG-MJ-1) 7 days in vase life Pink Tango Control D. TOG-MJ-1 ControlTOG-MJ-1 E.Tamara Sun Beam TOG-MJ-1 F. Control
Harvest Grading Bunching and sleeving Chemical pulse treatments Packing Cooling Dry or wet storage Transportation Marketing Postharvest handling of cut flowers
Postharvest vase solutions Vase solutions typically contain: Low concentrations of sugar (0.5-2%) A biocide [usually hydroxyquinoline (HQC) or TOG] Citric acid (300 ppm) to keep a low pH.
Handling requirements of some representative cut flowers Anthurium * Storage at 10-12 C. * Prevent mechanical damage by wrapping with plastic sleeves and fill-packing boxes with shredded paper.
Roses Pulse treatments with fungicides (vinclozolin, iprodione, copper) against Botrytis cinerea. Storage at low temperature (0-2 C) without water condensation. Usually, not treated with sugar or ethylene inhibitors. Add bleach to the vase solution.
Gerbera Are long lasting (till 20 days). Add bleach to vase solution Trim stems every few days
Lilium Pulse treatment with GA and STS. Add bleach to vase solution
Gladiolus Pulse with high concentrations of sugar (10%), STS and a fungicide.