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In Vitro Pollen Responses of Two Birch Species to Acidity and Temperature

Faculty of Forestry, Univ. of New Brunswick, Fredericton, NB Canada E3B 5A3;

R. M. Cox^*

Natural Resources Canada, P.O. Box 4000, Fredericton, NB Canada E3B 5P7.

^* Corresponding author.

ABSTRACT

Paper birch (Betula papyrifera Marsh.) and mountain paper birch (Betula cordifolia Regel) near the Bay of Fundy coast frequently intercept acidic advection marine fogs. Chemical deposition by these fogs is thought to be a factor contributing to the observed foliar browning symptoms 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 routinely found in the fog. The combined effect of temperature with acidity was also examined. Pollen germination in both species was inhibited below pH 5.6 (P < 0.0001) and the effect of incubation temperature was 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 °C for B. papyrifera and 21 °C for B. cordifolia.

(current address, Operations Branch, Dep. of Environ., P.O. Box 6000, Fredericton, NB Canada E3B 5H1)

Received for publication July 20, 1992.