Historical considerations: In 1609, a Belgian chemist discovered that gases released from heated coal could produce a flame. Nearly 200 years passed before a German engineer constructed a manufacturing facility to produce gas to light homes, businesses and streets. Commercial production and use of illuminating, coal, or manufactured gas became routine in industrialized countries during the 1800s.

In 1864, a report showed that shade trees located near leaking underground illuminating gas pipes that serviced street lamps defoliated. But it wasn't until 1901 that ethylene was identified as the active component of illuminating gas causing plant growth disorders. What led to the ethylene discovery was the observation that pea seedlings grew horizontally in greenhouses contaminated with this gas, but grew upright when fresh air was introduced into the same greenhouses.

Effects on plants/flowers (general): Countless articles have documented how this gas became known as the death hormone of plants or, as many believe, the major post-harvest enemy of the floral industry. Some negative plant responses to ethylene and examples of plant species affected include:

• Premature loss of foliage (ficus, azalea, rose, citrus)
• Premature loss of flowers (geranium, snapdragon, impatiens)
• Premature loss of fruit (holly, pepper, citrus)
• Premature flower death (carnation, kalanchoe, cattleya)
• Translucent petals (alstroemeria, gypsophila)
• Adventitious stem roots (tomato, mum)
• Petiole (leaf stalk) twisting or epinasty (poinsettia, tomato)
• Stem thickening (pea, mum, petunia, tomato)
• Foliage yellowing (mum, impatiens, petunia, lily)
• Premature fruit ripening (apple, pear, banana, kiwi, cucumber)

Information reprinted from SAF Flower and Plant Care Manual, (Society of American Florists: Alexandria, VA, 1994), pp. 147-150.