Plant-Damaging Pollutants in the Atmosphere, Vol.11, Issue 2

Home , Vinca minor

Dr, James L. Green ORNAMENTALS Sept.-Oct. 1987 Horticulture Department Vol.11, Issue 2 NORTHWEST OSU Pages 4-9 ARCHIVES Corvallis, OR 97331

PLANT-DAMAGING POLLUTANTS IN THE ATMOSPHERE

Ethylene

Ethylene is produced from many sources including industrial processes, exhaust from internal combustion engines, in propane gas mixtures and manufactured gas. It is a natural product of plants, especially damaged tissue and aging flowers and fruits and vegetables. The sensitivities of ornamental plants to ethylene, an air pollutant, throughout the life of the plant (production, storage, shipment, re-establishment) have been investigated by a number of researchers.

Ethylene toxicity symptoms were described for 52 plant species that were tested and classified according to their ethylene (C2H4) sensitivity by Woltering (1987). In general, flowering plants appeared more sensitive to ethylene treatment than did foliage plants. Ethylene toxicity symptoms observed included abscission of flowers, flower buds, inflorescences, and leaves, flower wilting, bud blasting, leaf yellowing, epinasty, and greater susceptibility to fungal infection.

Flowering plants exhibited abscission of flowers, flower buds or whole inflorescences after 24 hour exposure to ethylene (Woltering, 1987). Abscission of flowers, flower buds or of whole inflorescences occurred in about 65% of the species of flowering plants. In general, the mature flowers abscised at lower ethylene concentrations than did the flower buds; however, in Fuchsia the flower buds appeared to be more sensitive.

Leaf abscission was observed by Woltering (1987) in about 50% of the foliage and in about 30% of the flowering plants. Abscission of leaves generally occurred after 72 hours of exposure to ethylene. However, Beloperone, Clerodendron and Solanum exhibited leaf abscission after only 24 hours exposure. The older leaves usually abscised first at the lower ethylene concentrations. However in Capsicum annuum the younger leaves abscised preferentially, and in Dizygotheca and Browallia the oldest as well as the youngest leaves first showed abscission.

All fruit-bearing plants tested exhibited fruit-drop. Severe yellowing of leaves was only observed in Rhaphidophora aurea and Pelargonium zonale. Premature wilting of bowers was accompanied by bud blasting in some cases (i.e. Campanula, Kalanchoe, Pelargonium), and by abscission in the case of Cyclamen. A number of species showed an increase in fungal infections with increased ethylene exposure (i.e. Campanula, Chrysanthemum, Pelaronium, Saintpaulia). Chrysanthemum morifolium flowers, which are insensitive to ethylene from a physiological point of view, were severely damaged by fungal infection (i.e. Botrytis) when exposed to ethylene; it should be noted, however, that normal flower bud development does not occur when chrysanthemum is exposed to ethylene: Ethylene at concentrations as low as 0.018 to 0.072 ppm prevented flower bud development; crown buds did form, but were by-passed by vegetative shoots (Larson, etal., 1987).

The 52 species tested by Woltering (1987) were classified according to their ethylene toxicity symptoms and ethylene-sensitivity (Tables 1 & 2). Fuchsia hybrids and Hibiscus rose-sinensis were among the most sensitive. As well as differences between species, considerable differences in ethylene-sensitivity occurred between cultivars of the same species.

Additional classification of horticultural plants according to their ethylene-sensitivity is presented in Table 3 (Marousky and Harbaugh, 1986), Table 4 (Poole, 1986) and Table 5 (Hickman, etal., 1986).

AVOID ETHYLENE EXPOSURE:

Beware of confinement with fruits and vegetables:

Because fruits and vegetables may produce high concentrations of ethylene, plants should not be confined with them, i.e. plants should not be stored or shipped with fruits and vegetables. Table 6 (Poole, 1986) obtained from the University of Norway gives comparative ethylene producing capabilities of some vegetables and fruits. If a grower decides to risk storage/shipment of plants with fruits or vegetables, temperatures should be maintained as low as possible without low temperature damage to the plants and frequent air exchange should be maintained

Beware of faulty and unvented greenhouse heaters and C02 generators:

Tight greenhouses and unvented heaters often resulted in ethylene damaged plants rather than cost savings in 1986 (Larson, etal. 1987; Hickman, etal. 1986). During the winter of 1986 five different operations in California suffered severe crop losses from ethylene symptoms (Hickman, etal. 1986). In all the operations, standard vented gas heaters had recently been replaced with direct-fired unvented heaters because of potential 20-30% savings in energy costs. Air in these greenhouses was found to contain ethylene concentrations as high as 500 parts per billion.

Production of ethylene is not the only possible problem introduced by unvented heaters and C02 generators. Oxides of nitrogen may also be produced; high concentrations of oxides of nitrogen are more pernicious than ethylene because often the only symptom exhibited by plants is reduced vigor. Carbon monoxide, another product of incomplete combustion, is a gas that is extremely toxic to humans.

Table 1 (Woltering, 1987). FOLIAGE PLANTS: Ethylene toxicity symptoms and sensitivity classification after exposure to 0-15 microlitersfliter ethylene (0-15 ppm ethylene) for 24 or 72 hours in darkness at 20°C. C2H4 Toxicity Symptoms Abcission1

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Fatsia japonica ...... C ...... X ...... 2

Asparagus densiflorus 'Sprengeria' ...... D ...... 1 Asplenium nidus ...... 0 Capsicum annuum ...... C .... C ...... 2 Chamaedorea elegans ...... 0 Codiaeum variegatum ...... 0 Cordyline fruticosa ...... 0 Dieffenbachia'Marianne' ...... X ...... 1 Dizygotheca elegantissima ...... CD...... 3

Dracaena marginata ...... X...... 1

Dracaena sanderiana ...... X ...... 1

Eucharis grandiflora ...... X ...... 1 Euphorbia keysii ...... D ...... X ...... 3 Euphorbia pseudocactus .... D ...... X ...... 6 Ficus benjamina ...... C ...... 1 Ficus deltoidea ...... C .... C ...... X ...... 3 Ficus pumila ...... C ...... 2 Hedera canariensis 'Variegate' ...... C ...... 1 Nephrolepis exaltata ...... 0 Philodendron scandens oxycardium ...... C ...... 3

Rhaphidophora aurea ...... X ...... 3

Schefflera compacta ...... CD ...... X ...... 4

Scindapsus pictus ...... 0 Solanum pseudocapsicum .... C .... C ...... X ...... 7 Yucca elephantipis ...... X ...... 1

1Letters refer to the position of the abscission zones: C, at base of petiole; D, at base of the leaf blade. 2See Materials and Methods and Fig. 1 - Higher the number, the more sensitive the plant.

Table 2 (Woltering, 1987). FLOWERING PLANTS: Ethylene toxicity symptoms and sensitivity classification after exposure to 0-15 microliters/liter ethylene (0-15 ppm ethylene) for 24 or 72 hours in darkness at 20ºC. C2H4 Toxicity symptoms 1 Abscission

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Begonia semperflorens Fibrous begonia ...... X ... X .... Brassaia actinophylla Schefflera ...... X...... X Caladium hortulanum Caladium ...... X.... Capsicum annum 'Fireworks' Ornamental pepper ...... X.. ..X w ...... Chlorophytum comosum 'Variegatum Variegated spiderplant ...... X .... Coleus blumei Coleus ...... X ...... X .... Crassula argentea Jade plant ...... X ...... Dieffenbachia maculata 'Rudolph Roehrs' Golden dumbcane ...... X Episcia cupreata Flame violet ...... X...... Euphorbia pulcherrima Poinsettia ...... X .... Fittonia verschaffeltii Nerve plant ...... X ...... Hemigraphis alternata 'Exotica' Waffle plant ...... X.... Hoya carnosa 'Variegata' Variegated wax plant ...... X .... Impatiens wallerana Impatiens ...... X... X.... Iresine herbstii Chicken gizzard ...... X ...... X .... Philodendron scandens oxycardium Heartleaf philodendron ...... X ...... X Philea cadierei Aluminum plant ...... X....

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Table 5 (Hickmen, etal. 1986) Effects of ethylene on ornamental plants Name Sensitivity, - Symptoms Begonia spp. moderate, - flower drop Calceolaria crenatiflora moderate, - flower drop Chamaedorea elegans low, - leaf damage Chlorophytum comosum low, - if spot, burnt edges Cissus rhombifolia severe, - leaf and stem drop Coleus blumei moderate, - leaf yellowing Dieffenbachia amoena severe, - leaf scorch Dracaena fragrans severe, - burnt margins Euphorbia pulcherrima mod., - bract drop, epinasty Gardenia jasminoides moderate, - flower drop Gerbera jamesonii slight Impatiens sultanii severe, - if damage, flwr drop Matthiola incana moderate, - leaf fall Nephthytis 'Green Gold' moderate, - leaf death Pelargonium spp. very severe, - flower fall Petunia hybrids moderate, - if fall, flwr death Philodendron cordatum severe, - epinasty, leaf drop Pothos aureus severe, - leaf death Rhododendron 'Hexe' moderate, - loss of old lvs Sansevieria trifasciata slight Schefflera actinophylla severe, - leaf drop Schlumbergera bridgesii severe, - flower drop Streptocarpus hybrid severe, - flower fall Tagetes patula slight Tradescantia fluminensis severe, - leaf yellowing Tropaeolum majus severe, - leaf drop Zinnia elegans slight

Table 6 (from Poole, 1986). Ethylene production of some fruits and vegetables.

Very High Apples Cherrimoya Larson, etal (1987) listed the following 7 suggestions to Passion Sapota reduce the possibilities of incomplete combustion and High ethylene pollution in the greenhouse: Pears Nectarine Peaches Apricot 1) Locate heaters for minimum exposure to dust and high Avocado Rambutan humidity. Papaya Cantaloupe Medium 2) Provide adequate oxygen for combustion. Run a pipe or Banana Fig flexible hose from outside to the burner. One square inch of Plum Breadfruit opening/2500 BTU output is necessary. An 8" pipe has 50 Lychee Jackfruit square inches; this is needed for a heater producing 125,000 Mango Mangosteen BTU's. Screen off outside end of pipe or hose to prevent Honeydew Tomato closure from debris, birds, and insects.

Strawberry Bean 3) Never vent the exhaust into the greenhouse. Vents also Olive Eggplant should be tall enough to avoid emission of exhaust fumes Guava Okra into the greenhouse, and to avoid return of exhaust fumes Persimmon Pumpkin into the greenhouse through the ventilation system. Coconut Squash Cucumber Pineapple 4) Clean heating equipment (heater and fuel orifice) at least twice each year. Very Low Mandarin Cherry 5) Check color of flame: small yellow tips on flames from Tangerine Grapefruit propane gas and soft blue flames from natural gas indicate Lime Orange proper adjustment. Dates

6) Check regularly for gas leaks. Items 5 and 6 may require visits and advice from the fuel supplier or heater company.

7) Maintain proper ventilation.

Literature Cited:

Hickman, Gary, Richard Evans, and Michael Reid. 1986. Unvented heaters: False economy? Greenhouse Grower 4(8):75-76, August 1986.

Larson, Roy A., Joseph W. Love, and Sylvia M. Blankenship. 1987. North Carolina Flower Growers 31(4):3-7, August 1987.

Marousky, Frank J. and Brent K. Harbaugh. 1986. Deterioration of foliage plants during transit. Foliage News 11(6):1-9, June 1986.

Poole, R.T. 1986. Ethylenesensitivity and sources. Foliage Digest 9(11):8, November 1986.

Woltering, E.J. (Ministry of Agriculture and Fisheries, Sprenger Institute, P.O. Box 17, 6700 AA Wageningen, The Netherlands). 1987. Effects of ethylene on ornamental pot plants: classification. Scientia Horticulturae 31:283-294.

PLANT SENSITIVITY TO MERCURY VAPORS IN THE AIR

"When severe leaf-drop on acclimatized Ficus benjamina occurs suddenly after installation or repainting, the paint formulation should be obtained to determine whether mercury is present ... damage can occur to Ficus as much as a year later," according to Poole and Conover (1986, 1987). Damage to plants by mercury is not as prevalent today because its use is limited as other mildewcides are substituted for it. However, some paints still contain mercury, usually as phenylmercuric acetate (PMA). According to Poole and Conover, "Contacts with paint formulators indicate that mercury use is most common with formulators that service local commercial painting contractors and clientele. A commercial paint sold locally yielded a mercury vapor level of 0.030 mg/cubic meter during the first week." A Denver interiorscaper recorded 0.014 mg/cubic meter of mercury in a severely defoliating Ficus planting in a repainted lobby.

Of 14 genera tested by Poole and Conover,(Aglaonema, Aphelandra, Brassaia, Collinia, Codiaeum, Crossandra, Dieffenbachia, Dizygotheca, Ficus, Kalanchoe, Polyscias, Rosa, Schefflera, Spathiphyllum , only Ficus and Dieffenbachia were affected by paint containing mercury with the response being much greater with Ficus than with Dieffenbachia. Ficus experienced severe leaf drop within a week after placement in rooms painted with mercury-containing paints. Even after severe leaf drop, Ficus continued to produce new leaves, but these, too, soon dropped from the plant. Ficus in a room painted with paint containing more than twice the normal amount of mercury, lost leaves rapidly and eventually died. Lower leaves (more mature leaves) became chlorotic, then necrosis occurred.

The easiest way to solve the problem if mercury evolving paints have been used is to: 1) increase ventilation to dilute the mercury vapor concentration or 2) replace the Ficus with other plants such as Schefflera and Palms that tolerate mercury vapor.

Mercury vapor concentration can be determined by obtaining monitors manufactured by 3M Company, Occupational Health and Safety Products Division, Bldg. 230B, St. Paul, MN 55133 - telephone 1-800-328-1667 to determine the distributor nearest you. Price, including monitors and analysis, is approximately $300 for a box containing 5 each 3M Mercury Vapor Monitor #3600.

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