Effects of flooding on the germination of Lotus tenuis and Lotus corniculatus seeds. Their role in the differential distribution of both species in the Flooding Pampa, Buenos Aires, Argentina

摘要

Lotus tenuis (L. t.) and Lotus corniculatus (L. c.) were introduced as forage plants in the Flooding Pampa around 50 years ago. While L. t. has naturally colonized the frequently flooded habitats. L.c. has not shown the same expansion. In this paper we studied the tolerance to flooding of seeds of both species. The seeds were flooded during 7 weeks, in controlled conditions of temperature and light, and samples were taken at increasing time intervals. Germinative percentage (G. P.) of the seeds was taken as a measure of tolerance to flooding and it was found that although G. P. decreased with flooding time in both species, the soft seeds of L. c. lost viability earlier than those of L.t. With 49 days of flooding, hard seeds were the only ones that maintained the G.P. and were more frequent in L. t.. (aproximately 50% in L. t. and 6% in L. c, in 5 month old seeds). These characteristics probably play an important role in the capacity of L. t. of colonizing habitats that are periodically flooded