Factors Controlling Intumescence Development on Tomato Plants1

Abstract

Plants of the cultivated tomato, Lycopersicon esculentum Mill. cv. Oxheart, and of the wild tomato, L. hirsutum Humb. & Bonpl., were maintained in a growth chamber within small Plexiglas boxes to produce intumescence (oedema) injury. Severe injury occurred when plants were exposed to air from a pressurized laboratory supply and slight injury after exposure to air drawn from outside. Injury was greater on plants with 5 liters/min of air passing through the exposure boxes than with 1 liter/min. Severe but similar types of injury were observed at 30, 80, and 92% relative humidity (RH) levels. This is in contrast to previous research, which demonstrated that high humidity caused injury. Severe injury occurred at all irradiation levels evaluated—80, 240, and 400 µmol s −1 m −2 (PPFD)—for a 16-hour light period. Exposure to toxic air from the laboratory supply lines during either the light period or the dark period resulted in similar amounts of injury. Continuous exposure caused greater injury. Injury developed consistently under Cool-White fluorescent lamps with a UV-B absorbing barrier between the lamps and plants, but no injury occurred if the barrier was not present. UV-B irradiation of the air before it was supplied to the plant chamber did not prevent injury.