Effect of pappus removal on seed germination in Solidago ×niederederi (Asteraceae) and closely related species

Abstract

AbstractIn Solidago, the pappus, a modified calyx, protects ovary and fruit from predation and is strongly involved in anemochory. In this study, we aimed to test the hypothesis that the mechanical removal of pappus decreases the final percentage and speed of seed germination. We examined S. ×niederederi, a natural hybrid between invasive S. canadensis and native S. virgaurea, in comparison to its parental species and S. gigantea. We conducted a 21-day germination test in the laboratory, using 50 fruits with intact pappus and 50 fruits with removed pappus in four replicates, for each taxon. The statistical analysis demonstrated that the final percentage of germinated seeds was remarkably lower in the group of fruits with removed pappus in S. canadensis (p ≤ 0.05) and S. gigantea (p ≤ 0.05). Moreover, the speed of seed germination was also significantly lower after pappus removal in S. canadensis and S. gigantea, based on the Timson’s index (p ≤ 0.05). In the case of S. ×niederederi and S. virgaurea, the hypothesis was rejected. We assumed that the small size of the cypselae could be responsible for the negative effect of pappus removal on seed germination.