Effects of fertilizer on the amphicarpic traits of Persicaria thunbergii

Abstract

This study was performed to investigate the effects of fertilizer on the amphicarpic traits of Persicaria thunbergii in a mesocosm experiment. Three fertilizer levels were applied for different lengths of time: no fertilization, fertilization at eight-week intervals, and at four-week intervals. I compared the RGR and biomass allocation of seedlings from aerial seeds (SA) and subterranean seeds (SS) then investigated the flowering time and the seed production traits of P. thunbergii according to fertilizer levels. The results showed that RGR, biomass allocation and total biomass were not different between SS and SA at all levels. For the results of flowering time, aerial flowering started earlier than subterranean flowering unlike with other amphicarpic plants. This indicates that the productive strategy of P. thunbergii differs from other amphicarpic plants. Subterranean seed allocation and the number of subterranean seeds were stable regardless of fertilizer levels whereas aerial seed allocation decreased with the increase of fertilizer level and the number of aerial seeds per biomass with low fertilizer was significantly higher than at other levels. P. thunbergii showed a different trait of seed production: subterranean seeds appeared to play a role in retaining the mother-site while aerial seeds escaped the site conditions of low fertilizer. In conclusion, SA and SS showed similar life-history strategies according to fertilizer levels. The different traits of the two types of seed production would be increased survivability. Finally, the difference in the productive strategy of P. thunbergii would enable it to adapt to wetland habitats unlike other amphicarpic plants that inhabit arid areas.