IN-VITRO POLLEN RESPONSES OF 2 BIRCH SPECIES TO ACIDITY AND TEMPERATURE

Paper birch (Betula papyrifera Marsh.) and mountain paper birch (Betul a cordifolia Regel) near the Bay of Fundy coast frequently intercept a cidic advection marine fogs. Chemical deposition by these fogs is thou ght to be a factor contributing to the observed foliar browning sympto ms associated with a marked deterioration of these trees in the area. In vitro experiments were performed to test whether pollen germination in these two birch species would be affected by acidity at levels rou tinely found in the fog. The combined effect of temperature with acidi ty was also examined. Pollen germination in both species was inhibited below pH 5.6 (P < 0.0001) and the effect of incubation temperature wa s also significant (P < 0.01) in both species. There was no difference in in vitro pollen germination between species (P > 0.05) in response to acidity, based on combined data from 12 trees of each; the optimum germination temperature was 22-degrees-C for B. papyrifera and 21-deg rees-C for B. cordifolia.