Fungi-mediated mortality of seeds of two old-field plant species1

Abstract

Orrock, J. L. (Department of Ecology, Evolution, and Organismal Biology, Iowa State University, Ames, IA 50011) and E. I. Damschen (Department of Zoology, North Carolina State University, Raleigh, NC 27695). Fungi-mediated mortality of seeds of two oldfield plant species. J. Torrey Bot. Soc. 132: 613–617. 2005.—Fungi are a significant source of seed mortality. Although the seeds of pokeweed, Phytolacca americana, are known to contain antifungal compounds, it is unknown if these compounds confer the presumed benefit of increased persistence of P. americana seeds in soil compared to seeds of potential competitors. We buried seeds of P. americana with seeds of a sympatric species, Chamaecrista fasciculata, that is not known to exhibit antifungal properties. Half of the buried seeds were treated with a fungicide. After three months, seeds were exhumed. Treatment of buried seeds with fungicide significantly increased the number of intact C. fasciculata seeds recovered (82% recovered with fungicide addition, 39% recovered from controls). Recovery of intact P. americana seeds was 100% for both control and fungicide treatments. Results from a complementary experiment using non-buried seeds in a growth chamber experiment confirmed that P. americana was much less susceptible to fungal attack compared to C. fasciculata. Our work demonstrates that the antifungal properties of P. americana significantly improved survival of P. americana seeds in the seedbank. Moreover, this increased survival may promote P. americana persistence in communities where species without antifungal properties, such as C. fasciculata, also exist.