Evaluation of Di-1-p-Menthene as Antiozonant on Bel-W3 Tobacco Plants, as Compared with Ethylenediurea

Tropospheric ozone (O-3) has long been documented to cause an injury to plants, but a plants' protectant, widely applicable in agronomical practice, does not exist. We evaluated the potential antiozonate efficacy of the antitranspirant di-1-p-menthene (Vapor Gard) compared with ethylenediurea (EDU) on Bel-W3 tobacco plants. Plants were treated either with water, or by EDU (10, 100, and 500 mg dm (3)), or by vapor (1, 5, 10, and 50 ml dm(-3)) and were exposed either to O-3-enriched (90 ppb) or O-3-free air, for 12 days and 8 h day(-1). EDU when applied at 10 mg dm(-3) did not protect the plants against O3, but when applied at 100 and 500 mg dm(-3) offered a significant protection to the plants. Vapor, when applied at 1 ml dm(-3) did not protect the plants against O-3, neither by terms of foliar visible injury nor by terms of aboveground biomass. In addition, when applied at 10 and 50 ml dm(-3) caused phytotoxicity to all the plants, which it was expressed as necrotic spots on the leaves' surface, misshaping of the leaves, or short plants' height. It is obvious that vapor does not protect Bel-W3 tobacco plants against O-3. The antiozonate role of di-1-p-menthene is species-specific and probably occurs only under short-term exposures.