HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hughes, R. N. Articles by Cox, R. M. Search for Related Content PubMed Articles by Hughes, R. N. Articles by Cox, R. M. Agricola Articles by Hughes, R. N. Articles by Cox, R. M.

Acidic Fog and Temperature Effects on Stigmatic Receptivity in Two Birch Species

Air Quality Section, Operations Branch, New Brunswick Dep. of the Environ., P.O. Box 6000, Fredericton, NB, Canada E3B 5H1;

R. M. Cox^*

Natural Resources Canada-Canadian Forest Service, P.O. Box 4000, Fredericton, NB, Canada E3B 5P7.

^* Corresponding author (rcox{at}fcmr.forestry.ca).

ABSTRACT

Factorial assays were performed to determine the effects of simulated acid fog (SAF) and temperature on stigmatic receptivity in two birch species. Excised reproductive branches were sampled from representative individuals of mountain paper birch (Betula cordifolia Regel.) and paper birch (Betula papyrifera Marsh.) in populations adjacent to the Bay of Fundy, New Brunswick, Canada. Since 1979 these trees have exhibited branch dieback in association with abnormal foliar browning symptoms. This browning has been linked with acidity and nitrate deposited by fog, which is frequent in the area. In general, experimental results indicated that pollen germination increased with temperature, but pH effects were less obvious. Similarly, pollen tube growth responded positively to temperature and was little affected by fog acidity. ANOVA tests indicated a significant difference (P < 0.05) between species in their pollen germination response only at 12°C, and not at the other three temperatures tested. For pollen tube growth, significant differences between species (P < 0.05) were demonstrated at 12 and 22°C. A significant pH effect was demonstrated at 27°C for germination, while pH effects on tube growth were significant at 27 and 12°C (P < 0.01). A response surface regression analysis indicated that acidity significantly affected pollen germination in mountain paper birch (P < 0.001) but not in paper birch. Temperature was not a significant factor for in vivo pollen germination in either species. For pollen tube growth, however, temperature was more important than pH and produced highly significant effects in both species (P < 0.001). Acidity was also a significant factor in pollen tube growth for paper birch.