The flowering plants in these photos were in a greenhouse that had a furnace with a cracked heat exchanger causing the furnace to malfunction. Flowers withered and dropped. Geranium flowers blasted.
A malfunctioning furnace can release pollutants such as ethylene. Ethylene is a colorless, odorless gas that is responsible for beneficial and undesirable effects in greenhouse crops. Ethylene can prevent plants from flowering, shorten internode length, increase branching, initiate fruit ripening, cause leaf and flower senescence and abscission, leaf chlorosis (yellowing), and improve adventitious rooting. Some crops are relatively insensitive to ethylene while others are very sensitive such as tomato plants, which can be used as indicator plants in the greenhouse.
Ethylene damage commonly results in leaf curling, epinasty (leaves bending downwards from the petiole) and flower drop. Sudden loss of flowers (usually close to the furnace) is typical of ethylene injury.
For more information, see: Ethylene in the Greenhouse E-Gro Alert http://www.e-gro.org/pdf/2015_415.pdf
