Pulse Treatment to Inhibit Stem Bending

Vase life of several gerbera cultivars is often terminated by the occurrence of stem bending. While bacteria in the vase water leading to blocked xylem and reduced water uptake has been causally related to stem bending, other hypotheses for the cause of bending include lack of mechanical support due to failure or weakness in the stem cells. This research looked at the effectiveness of using a pulse treatment with calcium ions, which could increase the cell wall stiffness. Other components of the pulse treatments included antimicrobial compounds, surfactants, sucrose and salts.

While the primary cultivar used for this experiment was ‘Tamara’, several other cultivars were included; some more prone to stem bending, some less, based on preliminary experiments. Chemical combinations were either included in the vase water at the onset of vase life and not replenished, or applied for a 24-hour pulse directly after harvest.

 

This research showed delayed stem bending with a 24-hour pulse treatment at 20C with a solution containing 25 or 50 mM calcium chloride and 25g/L sucrose, together with a citric acid/K2HPO4 buffer at pH 3.5. Observation of individual components included: 1) A 24-hour pulse with calcium and potassium salts delayed stem bending, 2) Antimicrobial surfactants tested did not delay stem bending, 3) Sucrose in the pulse solution delayed stem bending, even when applied without and antimicrobial compound, and 4) Temporary dehydration drastically reduced stem bending.

Perik, R.R.J., D. Raze, A. Ferrante and W.G. van Doorn, 2014. Stem bending in cut Gerbera jamesonii flowers: Effects of a pulse treatment with sucrose and calcium ions. Postharvest Biology and Technology, 98 pp. 7-13. 

Fresh cut flowers are highly perishable, and research has shown that short vase life is a primary purchasing barrier for consumers. Not only does it decrease customer satisfaction, it also discourages repeat purchases. Research has also demonstrated that for potted plants, a guarantee decreased consumers’ perceived risk and improved consumers’ perceptions of the floriculture products’ quality. This research at the University of Minnesota looked at the impact of guarantees on consumers cut flower purchases in general and their willingness to pay for cut flower guarantees.

The research endeavor started with two pre-study focus groups whose responses to open-ended questions guided the development of the formal survey questionnaire. Next, a choice experiment was set up. Mixed flower arrangements and single-species arrangements were selected as the target products. The attributes of longevity, guarantee, price, use (for self or for gift) and flower arrangement type were considered using 24 choice scenarios. For each scenario, participants were shown images of the cut flower arrangements and were asked to make one of three choices: Arrangement A, Arrangement B, or Neither. Following the choice experiment, participants completed a survey questionnaire asking about attitudes toward cut flower longevities, guarantees and socio-demographic data.Fifty-five percent of the 525 research participants were women and the mean age was 43. Most were college-educated and came from a two- or three-member household. 

The presence of a guarantee increased the probability that participants selected the cut flower arrangement for both mixed and single-flower. They were also willing to pay a premium for a guarantee and they were willing to pay more for longevity of the flowers (as labeled).

The research also allowed for cluster analysis, which divided the participants into three clusters: guarantee seekers, value-conscious consumers and spenders. The socio-demographic descriptions of the clusters are intriguing, whereas the value-conscious consumers were mostly older women (compared to the other two groups) and spenders included more men, more people not in a relationship had a higher interest in guarantees on more expensive arrangements.

The researchers acknowledge predicting longevity and, furthermore, offering a guarantee, can be a challenge. They suggest that retailers 1) Source product from businesses with superior production and postharvest handling practices, 2) Educate staff on proper care of cut flowers from product arrival to post-sale, 3) Provide consumers with clear care instructions, and 4) Strive to promote an accurate longevity so that customers have reasonable expectations and dissatisfaction can be avoided. 

Rihn, A.L., Y. Chengyan, C. Hall, and B. Behe, 2014. Consumer Preferences for Longevity Information and Guarantees on Cut Flower Arrangements, HortScience, 49(6) pp. 769-778. 


Methods for Ethylene Control

Ethylene is a plant growth regulator involved in a variety of physiological processes including germination, growth, floral initiation and opening, senescence, abscission and fruit ripening. Responses to ethylene vary widely by plant species. Much is known about ethylene at the biochemical and genetic levels and numerous strategies have been developed to reduce ethylene production or inhibit its action to prolong flower postharvest performance. 

Genetic Strategies
Genetic modification of genes such as ETR1 and EIN2, which have been identified as part of the ethylene signaling pathway, have been successful in enhancing postharvest performance, but there are several barriers to commercialization of genetic transformation in ornamentals. Some barriers include cost, complexity of the regulatory process and varied levels of acceptance across world markets.

Environmental Strategies
Reducing exposure is a key environmental approach. Removal, oxidation and absorption are three main approaches to reduce ethylene levels. Removal can be accomplished through adequate ventilation, membranes for filtration, small sachets, films for modified atmosphere and activated carbon. Oxidation relies on using an inert matrix impregnated with potassium permanganate. Reduced air temperature and ventilation are commonly used during postharvest storage and transport, often in combination with adsorbers or oxidizers.

Chemical Strategies
While ethylene biosynthesis inhibitors lead to the reduction of endogenous ethylene, the compounds are often too expensive for practical use and therefore used mostly in research. Ethylene action inhibitors are more commonly used to in the trade, including silver thiosulfate and 1-MCP (marketed under the trade names EthylBloc and SmartFresh). 1-MCP, was the first patented non-toxic ethylene action inhibitor, but there are application barriers to it as well, including its gaseous state and reduced effectiveness at low temperatures (0-5C). New application methods are continuing to be developed and show promise, including a sachet that is dipped in water just prior to packing in a box, releasing the 1-MCP into the box as the water diffused through the sachet.

Scariot, V., R. Paradiso, H. Rogers, and S. De Pascale, 2014. Ethylene control in cut flowers: Classical and innovative approaches. Postharvest Biology and Technology, 97 pp. 83-92.

Megan Bame

Megan Bame is a freelance writer in Salisbury, North Carolina. Contact her at [email protected]