Plasticity in Plant Size and Architecture in Rhizome‐Derived vs. Seed‐Derived Solidago and Aster

Abstract

Old—field perennials of the genera Aster and Solidago, known to have long and short rhizomes, respectively, are expected to represent two types of genet architectures. We collected these plants at different field sites and grew their seeds and rhizomes in loose and compact soils to investigate the following questions about size and architectural plasticity in these clonal perennials: (1) to what extent do plant size and architecture vary among environments and within taxa, (2) does such variation obscure the differences in rhizome length and architecture between taxa, and (3) because these plants regenerate by clonal growth and sexual reproduction, how does mode of regeneration affect this variation? In all fields sites as well as in the contrasting experimental environments Aster and Solidago had similar size (e.g., shoot height and plant mass) but different architecture. Whereas Aster always produced long rhizomes and much—branched shoots with few main—stem leaves, Solidago produced short rhizomes and little—branched shoots with many main—stem leaves. Size variation among environments was large in both genera. Architecture was influenced by environment in Aster but not in Solidago. Phenotypic variation for size and architectural characters among populations and families within genera was small. In both genera, plants grown from rhizomes and from seeds of the same (maternal) parents had similar mean performance, but phenotypic variation among environments was greater for rhizome—derived than for seed—derived plants. We conclude that in these plants the environment influences variation in architecture less strongly than it affects variation in size. Because differences among populations and families were also small, the two taxa Aster and Solidago are well characterized by their respective plant architecture. We suggest that the influence of mode of reproduction on phenotypic flexibility may reflect a stronger architectural “blueprint” in seed—derived plants (less flexible) as compared with rhizome—derived plants (more flexible).