Fusicoccin and Air Pollutant Injury to Plants : Evidence for Enhancement of SO(2) but Not O(3) Injury.

Garden peas (Pisum sativum L. cv Alsweet) and a tomato mutant (Lycopersicon esculentum Mill. var flacca) were sprayed with fusicoccin, a fungal toxin affecting membrane transport properties, before exposure to SO(2) or O(3). Tomatoes treated with 10 micromolar fusicoccin and exposed to SO(2) (0.6 microliter per liter for 2 hours) exhibited twice as much foliar necrosis as untreated plants exposed to SO(2). Peas treated with fusicoccin and exposed to SO(2) (0.7 to 1.0 microliter per liter for 2 hours) exhibited 2 to 6 times more injury than untreated plants exposed to SO(2). Peas treated with fusicoccin and exposed to O(3) had less injury than untreated plants exposed to O(3) (0.1 to 0.3 microliter per liter for 2 hours). Several lines of evidence suggested that the fusicoccin enhancement of SO(2) injury is not the result of increased gas exchange, i.e. the tomato mutant has permanently open stomata under all conditions, and in peas fusicoccin had no effect on SO(2) or H(2)O flux in plants exposed to 0.12 microliter per liter SO(2). However, a 21% greater leaf conductance in fusicoccin treated versus untreated plants indicated the possibility of some differences in gas exchange for peas exposed to 1.0 microliter per liter SO(2).