COMBINATION OF UV-B AND OZONE REDUCES POLLEN-TUBE GROWTH MORE THAN EITHER STRESS ALONE

The rate of in vitro Nicotiana tabacum L. "Bel-W3" pollen tube growth was reduced 62 and 44%, respectively, when pollen tubes were exposed to 120 ppb ozone (O3) for 3 hr or 300 μW/cm2 ultraviolet-B (u.v.-B) radiation for 30 min. Petunia hybrida Vilm. "White Cascade" pollen tube growth was reduced 34 and 59%, respectively, upon exposure to O3 or u.v.-B at the above doses. The combination of u.v.-B at 300 μW/cm2 for 30 min, followed by O3 at 120 ppb for 3 hr, reduced pollen tube growth by 79% for "Bel-W3" and 75% for "White Cascade". The effect appeared to be additive, implying that different target areas may be affected by the two stressors. In the Northeast, plants are exposed to both u.v.-B and O3 during the normal growing season. This may result in an unexpectedly higher stress on the reproductive system than had been previously suspected based on these two stressors acting individually. © 1990.