Differences between individuals collected from sun and
shade populations could result from either somatic or
genetic differences, particularly in populations of
perennial plants. Our objective in this study was to separate
somatic from genetic differences. We collected
Anthoxanthum odoratum and Plantago lanceolata from sun
and
shade populations and made measurements on both
vegetatively propagated clones and seed progeny from each
clone. The parental populations differed in a wide
range of physiological and morphological traits. However, only
photosynthetic capacity was significantly different
between both the original sun and shade populations and their
seed progeny. In both species, plants from the sun
population had higher photosynthetic capacities than those
from the shade population when grown in a common
environment. This demonstrates that there was genetic
differentiation between the sun and shade populations.
Photosynthetic capacity of parents and offspring also
differed, suggesting a somatic effect. Since many of the
original clones were virus-infected, but all but one of the
offspring were virus-free, this might have been a result of
virus infection. However, in spite of the fact that the
parents and offspring clones were propagated vegetatively
so that the plants were at the same developmental stage
at the time of measurement, we cannot rule out the possibility
that differences in age of cell lines could also have been a factor.