First observation of true vivipary in Grindelia squarrosa (Asteraceae)

Abstract

In flowering plants, true vivipary is defined as the precocious seed germination and the growth of the embryo to a considerable size before dispersal. True vivipary occurs mostly in mangroves and is very rare in Asteraceae. In this study, we present the first observation of true vivipary in Grindelia squarrosa, a North American member of Asteraceae, from a new locality in Poland. We examined 50 fruiting capitula which were collected in October 2020 in Brzegi, southern Poland. True vivipary occurred in 90% of capitula; however, the number of germinated seeds was low (3.42 on average) and very variable (CV = 106%). Seed germination was found only in fruits developed from disc flowers. We presumed that precocious seed germination in G. squarrosa was induced by prolonged rainfall. The importance of true vivipary in naturalization and invasion of G. squarrosa as well as the involvement of viviparous seedlings in autochory should be further explored.