Relative effectiveness of ethylenediurea, and constitutent amounts of urea and phenylurea in ethylenediurea, in prevention of ozone injury to tobacco

The relative effectiveness of ethylene diurea (EDU), and constituent amounts of urea (U) and phenylurea (PU) in EDU, in prevention of ozone injury to tobacco (Nicotiana tabacum) leaves was determined in greenhouse exposure chambers. Four-leaf stage seedlings of tobacco cultivars Bel-W3 (ozone-sensitive) and Bel-B (ozone-tolerant) were either sprayed with water (controls), EDU (300 mg/litre), U (70 mg/litre), or PU (159 mg/litre) 24 h before exposure to charcoal-filtered (CF) air or CF plus ozone at 80±5 ppb for 7 h/day for 5 or 6 days. None of the treatments adversely affected Bel-W3 or Bel-B plants in CF air. Control or treated Bel-B plants in ozone were not affected. Ozone injury on Bel-W3 plants was evaluated daily, using the oldest two lower leaves (one and two). EDU was the most effective treatment, diminishing slightly with length of ozone exposure. U-treated plants experienced as much or more ozone injury than the non-treated controls. PU reduced ozone injury significantly, but was not as effective as EDU. When Bel-W3 plants were treated with 300 mg/litre EDU or PU and exposed to ozone, both compounds were equally effective in preventing ozone injury