How Do the Effects of Ethylene on Flower Quality Impact Floriculture?

• Ethylene is one of the main factors affecting flower and ornamental plant quality and longevity in the entire floriculture supply chain.
• Ethylene inhibits growth, branching, flower bud abortion, and leaf and flower abscission, reducing the quality and longevity of floriculture products.
• Floriculturists can increase ROI by monitoring and reducing ethylene levels in greenhouses, storage, distribution, and transport facilities.

One of the most common factors affecting the quality of cut flowers and potted plants in floriculture is ethylene. The phytohormone can lead to losses by impacting quality throughout the supply chain. However, not all effects of ethylene are harmful. In this article, you will discover how ethylene influences floriculture products and how its adverse effects can be avoided.

Figure 1: “Ethylene, a plant hormone that causes flowers to wilt and fade and accelerates the drop of buds, petals, and leaves,” American Floral Endowment, 2023. (Image credits: https://endowment.org/news/keeping-flowers-fresh-new-afe-funded-research-exploring-alternatives-to-ethylene-inhibitors) 

Flower and Plant Quality

Ornamental flowers—Bedded and potted ornamental plants, especially cut flowers, are fragile, and quality monitoring is necessary throughout the supply chain. Some quality issues can include abscission, weak or bent stems, wilting, pests, and diseases. Nearly 20-30% of cut flowers are lost in the postharvest stages.

Ethylene is one of the significant factors affecting floriculture products. Other factors can include temperature, light, nutrition, irrigation, water quality, pests, diseases, and flower maturity.

Ethylene

Ethylene is a natural phytohormone produced by plants. At room temperature, it is a colorless and odorless gas. It disperses quickly in the air and can harm neighboring plants. Moreover, it is autocatalytic and triggers more ethylene production in flowers and fruits.

Ethylene is active and can influence plants in small quantities of 1 part per billion (ppb) or 0.001 parts per million (ppm). It has a role in growth and development throughout an ornamental flower plant’s life cycle, starting from germination. However, ethylene is usually considered a contaminant in the floriculture supply chain as it promotes branching, inhibits growth extension, and senescence of leaves, flower buds, and flowers.

Ethylene effects will depend on the following factors:

• Concentration of ethylene.
• Duration of ethylene exposure.
• Temperature during plant or flower exposure to ethylene.
• Species sensitivity to ethylene.

Higher ethylene concentrations, longer exposure durations, and higher temperatures cause more harm to plants and cut flowers.

Ethylene produced by individual plants is not enough to harm its commercial products. However, creating ethylene hotspots and artificial sources can raise ethylene concentrations enough to start deleterious effects.

The effects of ethylene in floriculture vary in different supply chain stages.

Figure 2. “Effects of 8 hours (short-term) of high ethylene exposure of 1 ppm. Leaf and flower abscission on Portulaca (A) and Cuphea (B), respectively,” Leatherwood and Mattson. (Image credits: Cornell CALS)

Adverse Effects of Ethylene in Greenhouses

Ethylene can be harmful and beneficial in greenhouses during the plant’s growth stages.

Incomplete fuel combustion in heaters causes lower ethylene contamination of <0.1 ppm over extended periods, which can have subtle growth effects. The phytohormone results in plant growth inhibition, leaf twisting, and small flower bud abortion. Sensitivity to ethylene depends on species, so not all flowers are equally impacted. Poinsettia is not affected by exposure to 1 ppm ethylene for 24 hours, whereas 0.01 ppm exposure of Cuphea hyssopifolia for 24 hours results in all flowers getting abscised. Begonia, geranium, dianthus, fuchsia, hibiscus, impatiens, salvia, orchids, and petunia are also very sensitive to ethylene.

Plant responses to higher concentrations of ethylene > 0.1 ppm are more well-documented.

Short exposures can cause leaf and flower abscission, yellowing or chlorosis, or bent leaves (see Figure 2). Long-term exposure to high ethylene concentrations stunts plants, delays flowering, causes deformation or yellow leaves, increases branching, reduces flower scent, and leads to plant senescence. Table 1 gives specific symptoms of several species exposed for short and long durations.

Table 1: “Complete listing of all species tested and their response to short- and long-term ethylene exposure.  If the response appears at only a specific concentration, that will appear in the description,” Leatherwood and Mattson. (Credits: Cornell CALS)
Plant	Short-Term Response (After 72 hours)	Long-Term Response(After Several Weeks)
Bacopa’ Calypso Jumbo Lavender’	Slight leaf curling	Reduced overall growth, flower counts, and branching
Basil ‘Sweet Large Leaf’	No Change (N/C)	Increased branching
Begonia fibrous’ Cocktail Gin’	N/C	Reduced height, overall growth, flower count
Calendula’ Bon Bon Yellow’	N/C	Reduced height, overall growth
Calibrachoa’ Callie Dark Blue’	N/C	Reduced height and overall growth, increased branching
Coleus’ Stained Glassworks Copper’	N/C	Increased branching
Cuphea’ Allyson Heather’	Complete flower shattering after 24 hours at 0.01 and 0.05  ppm ethylene	Reduced flowering, increased branching
Dahlia ‘Carolina Orange’	N/C	Early flower senescence
Dianthus ‘Telstar Pink’	N/C	Reduced height, branching, overall growth, and flower counts
Fuchsia’ Trailing Dark Eyes’	Slight leaf curling, which increases with concentration	Reduced branching, overall growth, increased height, flower counts
Zonal Geranium ‘Rumba Fire’	Yellowing of stipules after 48 hours at 0.01 and 0.05 ppm ethylene	Increased flower counts
Gerbera’ Jaguar Formula Mix’	N/C	Leaves are flatter against the soil
Impatiens ‘Super Elfin XP White’	Slight leaf curling after 24 hours at 0.05 ppm ethylene	Reduced height, overall growth, flower size, and flower counts
Lobelia’ Riviera Blue Splash’	N/C	Reduced height, overall growth, and flower counts
French Marigold ‘Crested Bonanza Mix’	N/C	N/C
New Guinea Impatiens’ Sonic Deep Purple’	N/C	Reduced height, overall growth
Osteospermum ‘Asti Purple’	N/C	Reduced overall growth, increased branching
Pansy’ Delta Formula Mix’	N/C	Reduced height
Petunia multiflora prostrate single ‘Saguna Pastel Yellow’	Rapid senescence of open flowers 24 to 48 hours after exposure to 0.01 and 0.05 ppm ethylene	Reduced overall growth, flower size and flower counts, increased height and branching
Portulaca ‘Yubi Summer Joy Apricot’	Some leaf abscission within 24 hours of exposure to 0.05 ppm ethylene. Leaf abscission does not persist long-term	Reduced height and increased branching
Primula ‘Danova Select Mix’	N/C	Leaves are flatter against the soil
Rosemary ‘Arp’	N/C	Reduced branching
Sanvitalia’ Sundance Yellow’	N/C	N/C
Snapdragon’ Florini Amalia Yellow’	N/C	Reduced height & flower scent at 0.05 ppm ethylene
Torenia’ Clown Blue’	N/C	Reduced overall growth, height, and flower counts
Verbena’ Lannai Dark Red’	Slight leaf curling 24 hours after exposure to 0.05 ppm ethylene	Reduced height

 

Beneficial Effects of Ethylene in Greenhouses

Ethylene can be harmful when it is higher in concentration but is also applied externally to regulate growth and reproduction. Effects like growth inhibition, promotion of branching, and flower and bud senescence are sometimes necessary for ornamental plants. In these cases, ethylene is usually applied as a foliar spray of 250 to 500 ppm or drench at 20 to 40 ppm.

The timing of the application can be critical. If ethylene sprays are applied too early, they inhibit root formation, and when used too late, they delay flowering. Therefore, ethylene is applied after roots are well formed to promote branching and limit extensive vegetative growth. Small-scale trials to determine timing and concentrations for each crop are recommended to optimize ethylene application results.

Adverse Ethylene Effects in Later Supply Stages

Ethylene effects during transportation, storage, and distribution are invariably negative.

Cut flowers and potted plants can be exposed to ethylene levels of 100 ppb during transport and storage. Due to hotspot formation, brief exposures occur during loading, transport, or storage in sealed containers, which can affect flower and plant quality and longevity. Treatment with ethylene inhibitors like 1-MCP and silver thiosulfate (STS) keeps the hormone levels low. However, human safety is an issue with these chemicals, especially the latter, which can persist for many weeks.

In supermarkets, ethylene levels can be over 1000 ppb.

Even in the later stages of the supply chain, genetics matters in determining sensitivity to ethylene in cut flowers. Table 2 lists symptoms in various cut flowers due to ethylene exposure.

Table 2: “Typical symptoms of ethylene damage to popular cut flowers are listed below” Ebeling 2020. (Credits: https://floristsreview.com/ethylene-damage-in-flowers-and-plants/)

Reducing Unwanted Ethylene Effects

Knowing the sources is necessary to reduce the damage caused to floriculture by ethylene. For various reasons, ethylene levels in the supply chain can increase beyond natural production levels.

Sources of Ethylene

In greenhouses, heaters, especially gas-fired ones, produce ethylene. Insufficient oxygen supply to heaters, leading to incomplete combustion, can produce ethylene. Unvented heaters are popular for their higher efficiency but can cause ethylene buildup. Inadequate ventilation or a mixture of ambient air in the hot air distribution tube to reduce ethylene concentrations can also be problematic.

The presence of decaying plant material that produces ethylene naturally is another source of high concentrations in greenhouses.

In the later stages, hotspots of ethylene can form in transport, storage, and distribution centers, where the gas concentrations increase because flowers are stored with fruits or due to high-density packing. Moreover, machinery like forklifts and other equipment will release ethylene.

Cut flowers and plants also release ethylene when they are stressed, which can happen when they are being transported. Since ornamentals are shipped at high densities, ethylene can spread to whole batches.

Prevent Ethylene Production and Exposure

Once the source is identified, prevention is the best means to limit ethylene damage. Growers can take various steps to prevent ethylene buildup in greenhouses and the supply chain.

• In the greenhouse, heaters should be installed above and away from growing plants.
• If heaters and equipment are used, the area should be ventilated periodically.
• Separate loading docks from growing areas.
• Lowering temperatures and using ethylene inhibitors during shipping can inhibit plant ethylene production. Ventilation can also dilute concentrations in the air.
• Keep ethylene-sensitive species away from heavy machinery.
• Proper maintenance of heaters, distribution pipes, fuel lines, greenhouse vents, and any other machinery in the entire supply chain can check for cracks, leaks, and blockages that increase ethylene levels in the air.

Monitoring and Control of Ethylene

Growers and other stakeholders can also be proactive and monitor the atmosphere for any increase in ethylene so that they can control its levels. Checking for irregular growth and ethylene exposure signs may not be enough since symptoms can be similar to those caused by other factors.

Some standard methods of monitoring are as follows:

Use indicator plants: Use species that are very sensitive to even very low levels of ethylene, like Cuphea and tomato. Cuphea loses all its flowers, and tomatoes bend its leaves down within 24 hours of ethylene exposure of 0.01 ppm. The indicator plants should have no prior exposure to ethylene and should be well-distributed in the area to be tested.

Laboratory testing: A better method for ethylene detection is testing air samples at university or commercial laboratories. Obtain and follow instructions and use kits where available.

Use Gas analyzers: Several commercial gas sensors are available that analyze and give ethylene results in real-time. The advantage over laboratory tests is that air can be monitored onsite more frequently, making it less costly and a more efficient and consistent way of monitoring ethylene levels.

When higher levels of ethylene are detected, control measures like ventilation and checking of machinery and heaters can be undertaken to reduce the gas levels.

Gas Analyzers

The gas analyzers used for ethylene detection and monitoring must be accurate and reliable. Felix Instruments- Applied Food Science offers the F-900 Portable Ethylene Analyzer with an electrochemical sensor. It has a lower detection limit of 0.025 ppm (or 25 ppb), which makes it suitable for most ornamental species, except for very ethylene-sensitive ones like Cuphea. It is small, portable, user-friendly, doesn’t require special training for handling, and can be used in the entire floriculture supply chain to identify ethylene and cut related losses. Since floriculturists grow high-value cash crops, loss reduction can increase ROI considerably.

Sources

American Floral Endowment, 2023. Keeping Flowers Fresh: New AFE-Funded Research Exploring Alternatives to Ethylene Inhibitors. Retrieved from https://endowment.org/news/keeping-flowers-fresh-new-afe-funded-research-exploring-alternatives-to-ethylene-inhibitors)

 

Ebeling, M. (2020, Jul, 16). Ethylene Damage in Flowers and Plants. Retrieved from https://floristsreview.com/ethylene-damage-in-flowers-and-plants/

 

Leatherwood, R., and Mattson, N.S. (n.d.). Ethylene in the Greenhouse: Symptoms, Detection & Prevention. Retrieved from https://greenhouse.cornell.edu/crops-culture/ethylene-in-the-greenhouse-symptoms-detection-prevention/

 

Petrou, K.N. & Lacovidou, E. (2015). Cut flower waste management. Retrieved from https://www.researchgate.net/publication/360313425_Cut_flower_waste_management

 

Runkle, E. (2019, Jan). Ethylene in Floriculture. Retrieved from https://www.canr.msu.edu/floriculture/uploads/files/ethylene%20in%20floriculture.pdf