BONSER, STEPHEN P.* and MONICA A. GEBER. Department of Ecology and Evolutionary Biology, Corson Hall, Cornell University, Ithaca NY, 14853. - Growth form controls developmental and morphological responses to light quality in two annual plant species.
Environmental conditions can influence a plant’s rate of development
and induce morphological responses that may affect fitness. Plant
growth form can also constrain or promote developmental and
morphological responses, since plants of different growth form differ
in the placement and timing of production of vegetative and
reproductive modules. In this study, we examine how growth form
controls developmental and morphological responses, and fitness across
light environments in Brassica rapa and Arabidopsis
thaliana. Erect (wild type) and rosette (mutant) genotypes of
Brassica and rosette form genotypes (mutants differing in
traits related to rosette size) of Arabidopsis were grown in
high light (control) and green light filtered (spectral shade)
environments. Spectral shading reduced fitness and altered patterns of
development in genotypes of both species. Spectral shading induced a
shade avoidance response of increased vertical extension, although the
strength of this response was not consistent across all genotypes. For
example, hypocotyl extension was relatively greater in the rosette
form and internode extension was relatively greater in the erect form
of Brassica. Rosette genotypes (Brassica) and genotypes
with high rosette allocation (Arabidopsis) suffered relatively
high fitness reduction in spectral shade treatments. The results of
this study demonstrate that growth form can influence morphological
and developmental responses that may have important fitness
consequences across a range of environments.
Key words: Arabidopsis thaliana, Brassica rapa , development, fitness, morhological response