Pollen Chemosensitivity to Ozone and Peroxides

The sensitivity of pollen from seven plant species to ozone and the stable products of ozone treatment, such as hydrogen peroxide and tert-butylhydroperoxide, was tested using pollen autofluorescence and germination as assays. Total ozone doses corresponding to 0.15–5.0 ppm (l h) were applied. In the carotenoid-enriched pollen of Passiflora coerulea, Philadelphus grandiflorus, and Hemerocallis fulva, the treatment with low ozone doses (0.15 ppm) resulted in the disappearance of carotenoid fluorescence maxima in the region of 535–560 nm and the appearance of novel peaks, probably related to lipofuscins, in the region of 460–480 nm. Similar changes occurred one day after pollen treatment with peroxides. In the carotenoid-depleted pollen of Hippeastrum hybridum andPlantago major, the ozone treatment shifted a single peak at 480–490 nm toward the long- or short-wavelength region, depending on the ozone dose, and also changed (increased or decreased) the total fluorescence intensity. In anthocyanin-rich pollen of Papaver orientale and Petunia hybrida, neither ozone nor peroxides affected the spectrum pattern, though ozone enhanced fluorescence. Ozone and peroxides exerted opposite effects on pollen germination: ozone suppressed, whereas peroxide stimulated pollen tube growth. It is proposed that the damaging effect of ozone is not mediated by peroxide formation (which stimulates pollen germination), but rather is related to the direct oxidation of the pollen-wall components by O₃ itself or by the hydroxyl radicals thereby produced.