Survival and Aerenchyma Development under Flooded Conditions of 'Boltoniadecurrens', a Threatened Floodplain Species and 'Conyza canadensis', a Widely Distributed Competitor

摘要

Boltonia decurrens (Torrey and Gray) Wood (Asteraceae), a perennial floodplainspecies endemic to the Illinois River Valley, is threatened with extinction due to the destruction of natural wet prairie habitat and alteration of normal flood patterns. We compared the effect of varying flood periods on the growth and survival of B. decurrens with a co-occuring early successional species, Conyza canadensis (as Erigeron canadensis L.) Cronquist (Asteraceae), and investigated root morphology for potential mechanisms of flood tolerance. Boltonia decurrens was flood-tolerant, showing complete survival of plants through all flood treatments. Height was 80 percent and biomass was over 50 percent of control plants when flooded for 56 days, whereas 83 percent of flooded plants had begun flowering by the end of the experiment. Root aerenchyma of B. decurrens was extensive and increased in primary adventitious roots from 26 percent of root x.s. area for control plants to 49 percent under flooded conditions.