Comparison of Intraspecific Variations in the Reproduction and Photosynthesis of an Understory Herb, Arnica Cordifolia

Abstract

Intraspecific variations in the reproduction of individual ramets and monospecific patches of the understory herb Arnica cordifolia Hook. were compared with variations in photosynthesis and understory light conditions. Ramets and patches were compared from three microhabitats (open, intermediate, and shaded) that differed in daily integrated irradiance. Individual ramets from open microhabitats (> 12 MJ m−2 d−1) had 23% more total dry wt and produced twice as many seeds, when compared to ramets from shaded locations (< 5 MJ m−2 d−1). In addition, monospecific patches from open locations were 63% more dense, and estimates of seed and vegetative patch reproductive effort were 4 and 2 times greater, respectively, when compared to shaded plant patches. For all measurements, ramets and patches from intermediate understory locations (6–10 MJ m−2 d−1) were intermediate in reproductive capacity between those of open and shaded locations. In addition, A. cordifolia seeds from open microhabitats germinated significantly better (45%) than either intermediate or shaded location seeds under high light and only seeds from shaded microhabitats germinated (14%) in the dark. Compared to shaded location plants, the greater total dry weight and seed production of individual ramets and the greater estimated reproductive effort of patches from open locations corresponded to a greater maximum photosynthetic rate (16.9 μmoles m−2 s−1) and daily carbon gain (12.2 g m−2 d−1). Possibly, a greater photosynthetic capacity may make more photosynthetic resources available for reproduction by A. cordifolia plants in open locations. Thus, intraspecific variation in physiology may contribute to intraspecific variation in reproduction.

Above-ground biomass allocation by four understory vascular plant species in central Alberta Jack Pine, Pinus banksiana, forests

“…borealis suggests that conditions favorable for vegetative production also stimulate reproductive output in that species. Light conditions associated with high reproductive effort in two forest herbs (Aster acuminatus and Arnica cordifolia) were also associated with increased plant size (Pitelka et al 1980;Young 1983).…”