Reduction in tobacco pollen germination and tube elongation, induced by low levels of ozone.

Pollen of the ozone-sensitive tobacco variety Bel W-3 undergoes a reduction in germination rate and tube elongation when exposed to ozone. As little as 0.1 part of ozone per million for a 5.5-hour exposure period is sufficient to cause a 40 to 50 percent reduction in germination and a 50 percent reduction in pollen-tube elongation. Ozone causes these effects to approximately the same degree whether the pollen is exposed to ozone in vitro or agar disks, or in vivo when the intact plant is exposed. Exposure to ozone at a concentration of 1.0 part per million for more than 3 hours in vitro completely prevents germination of Bel W-3 pollen.