All plants used in this study were obtained from a site near the Melvin Price ... Dam, St. Charles County, Missouri (38052'06"N lat, 90012'22" long; elev, 140 m).
Am. Midl. Nat. 134:117-126
Survival and Aerenchyma Development under Hlooded Conditions of Boltonia decurrens, a Threatened Floodplain Species and Conyza canadensis, a Widely Distributed Competitor M. A. STOECKER ICI Seeds, Applied Physiology Group, PO. Box 500, Slater,Iowa 50244
M. SMITH AND E. D. MELTON Biology Department, Southern Illinois Universityat Edwardsville 62026 ABSTRACT.-Boltonia decurrens (Torrey and Gray) Wood (Asteraceae), a perennial floodplain species 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. decurrenswith a co-occurring early successional species, Conyza canadensis (as Erigeron canadensis L.) Cronquist (Asteraceae), and investigated root morphology for potential mechanisms of flood tolerance. Boltonia decurrenswas flood-tolerant, showing complete survival of plants through all flood treatments. Height was 80% and biomass was over 50% of control plants when flooded for 56 days, whereas 83% of flooded plants had begun flowering by the end of the experiment. Root aerenchyma of B. decurrenswas extensive and increased in primary adventitious roots from 26% of root x.s. area for control plants to 49% under flooded conditions. Conyza canadensis was flood-sensitive, with >50% reduction in survival. Aerenchyma was
