B. Heijne et al., EFFECTS OF ATMOSPHERIC AMMONIA AND AMMONIUM-SULFATE ON VESICULAR-ARBUSCULAR MYCORRHIZAL COLONIZATION IN 3 HEATHLAND SPECIES, New phytologist, 127(4), 1994, pp. 685-696
Three heathland species, Arnica montana L., Viola canina L. and Nardus
stricta L., were exposed to gaseous ammonia and artificial rain conta
ining ammonium sulphate for 11 wk. Plants infected with Glomus fascicu
latum (Thaxter sensu Gerdemann) Gerd. and Trappe grew faster than non-
mycorrhizal plants. Ammonia increased the shoot dry weight of both myc
orrhizal and non-mycorrhizal V. canina and mycorrhizal N. stricta. Onl
y mycorrhizal V. canina and non-mycorrhizal N. stricta grew faster whe
n supplied with increasing concentrations of ammonium sulphate. The ni
trogen tissue concentration, in all three species, was not influenced
by vesicular-arbuscular mycorrhiza (VAM), but increased when plants we
re treated with ammonia. Mycorrhizal and non-mycorrhizal N. stricta an
d mycorrhizal V. canina had a higher N tissue concentration when suppl
ied with ammonium sulphate. The phosphorus tissue concentration was hi
gher when plants were infected with VAM, but tended to be lower in the
presence of ammonia or ammonium sulphate. Mycorrhizal plants had high
er total amounts of N and P than non-mycorrhizal plants and plants tre
ated with ammonia had higher total amounts of N than non-treated plant
s. VAM colonization increased in all three species when treated with a
mmonia but was not affected by exposure to ammonium sulphate. Mycorrhi
za decreased the sensitivity of N. stricta to drought, while ammonia d
ecreased the sensitivity to drought for all three species. The effects
of additional nitrogen in relation to N/P ratios are discussed with r
espect to the ecological consequences for these heathland species.