Phenotypic plasticity in Philonotis fontana (Bryopsida : Bartramiaceae)

Gametophytes from six populations of the moss Philonotis fontana (Hedw.) Brid. were grown under two light and two water regimes in order to assess the effects of these environmental factors on gametophytic architecture and leaf and leaf-cell dimensions. Both light and water affected growth, but the light treatments had a greater effect, and on more characters, than did the water treatments. Significant population effects under common garden conditions point to genetic variation for several traits, and population x environmental treatment interactions demonstrated genetic variation for patterns of phenotypic plasticity, i.e. plants differed in their 'norms of reaction'. Variation among populations in leaf dimensions tended to have a strong genetic component (20-30% of the total variation), whereas cell dimensions showed relatively little genetic variation (<10% of the total).