Benghal Dayflower (Commelina benghalensis L.) in Agronomic Systems.

摘要

Benghal dayflower is an invasive, federal noxious weed and a serious threat to agronomic crop production in the southeastern United States. This weed is a native of tropical Asia, Africa and pacific islands and was introduced into Florida in early 1930s. Benghal dayflower possesses several physiological characteristics that aid in its survival and invasiveness. Extensive aerial and subterranean seed production, tolerance to commonly used herbicides including glyphosate, and ability to regenerate from stem fragments make Benghal dayflower extremely difficult to control. The present research was conducted to characterize Benghal dayflower responses to various environmental conditions. The responses allow prediction of Benghal dayflower invasiveness into various agronomic systems.;In the first series of experiments, Benghal dayflower seed viability was examined after exposure to high temperatures commonly found in hay bales and to simulated ruminant digestion. Ability of stem fragments to regenerate under different temperatures and soil depths was also tested. Measurement of temperatures in hay bales indicated that temperatures could reach 70 °C in the weeks following bailing. Seeds were non-viable within 1 day at 65 °C and within 14 days at 50 and 45 °C, indicating sensitivity to extremely high temperatures. It thus seemed unlikely that seeds captured in hay bales would remain viable and be spread during animal feeding. Seed viability might be expected with animal consumption of unbaled hay or with foraging.;Benghal dayflower seeds were more tolerant to ruminant digestion of 12 to 96 hours than seeds of other weed species and retained their viability. If viable seed were consumed, subsequent dispersal in manure would probably occur. In the case of stem fragments, regeneration occurred at 2 cm and 6 cm when aerial temperatures were about 25 °C. New roots developed at both soil depths, but leaf development was restricted at 6 cm and subterranean spathe development at 2 cm.;In the second series of experiments, long-term soil burial studies were conducted to examine longevity of Benghal dayflower seeds at different sites in North Carolina, Florida, and Georgia. Seed remained viable for a couple of years, and then declined. Viability was reduced to 10% at all locations after 36 months. This indicates that management programs must prevent seed production for at least 3 growing seasons to appreciably reduce the Benghal dayflower soil seedbank.;In the last series of experiments, Benghal dayflower growth and reproductive responses to differing environmental conditions were examined over a 56 d period. Plants produced greatest vegetative biomass at 35/28 °C day/night temperature. Flowering was suppressed by 3 days at 35/28 °C and by 7 days at 30/22 °C with the night interruption. However, aerial and below ground reproduction was influenced very little by changes in photoperiod. In the second part of this experiment, reduced nutrient and shading markedly reduced vegetative biomass of plants. Aerial and subterranean spathe production expressed different degrees of adjustment to suboptimal conditions. Aerial reproduction was reduced at sub-optimal conditions, but belowground reproduction remained relatively stable. The results therefore indicate that Benghal dayflower would persist in agronomic systems even under reduced resource availability.