PHENOTYPIC PLASTICITY IN LEAVES OF 4 SPECIES OF ARCTIC FESTUCA (POACEAE)

Leaf phenotypic plasticity of 12 morphological, anatomical, and growth traits was investigated using four species of arctic Festuca (F. baff inensis, F. brachyphylla, F. edlundiae, and F. hyperborea). Plants col lected around 78 degrees N in the Canadian Arctic Archipelago were gro wn for 10 weeks at the University of Toronto in growth chambers in con tinuous light, under four regimes of temperature and moisture. Signifi cant differences were found between leaves at the time of field collec tion and leaves of the same plant at the end of the experiment in (i) leaf blade length, (ii) surface vestiture, both in trichome density an d angle of the trichomes to the blade surface, and (iii) characters se en in leaf cross sections: blade width, rib thickness, and inter-rib t hickness. The four species responded similarly to the experimental con ditions, indicating that most of these changes represent part of the d evelopmentally inevitable component of plasticity rather than species- specific adaptations. Trichome density was the only characteristic for which species showed different patterns of response, with a unique pa ttern of response in F. edlundiae. This and certain growth traits supp ort the taxonomic status of this newly recognized species. The signifi cant effects of temperature and to a lesser degree, water treatments o n these leaf anatomical traits indicate that they should be used with caution for the purposes of taxonomy and identification.