Assessing the Lethal Effects of Glyphosphate on Amur Honeysuckle (Lonicera maackii) Stem Tissue
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In the past 50 years, the introduced Asiatic shrub Amur honeysuckle, Lonicera maackii, has invaded native habitats and out-competed native plant species, causing a decrease of plant biodiversity in the Eastern United States. Due to honeysuckle's resilience, extensive growth, and lack of natural enemies it has proven a difficult species to eradicate. Since no biological controls currently exist, glyphosate, the active ingredient in the herbicide Roundup, seems to be the easiest way to kill the plant; however, lethality has shown to be most effective during certain times of the year. The purpose of this project was to further explore glyphosate's lethal effects on the physiology and metabolism of Amur honeysuckle's stem tissue. Experiments measuring tissue viability with carboxyfluorescein diacetate (CFDA) and phenosafranin, the plant water content, and shikimic acid levels were used to determine plant death. CFDA, which is a viability stain, enabled the effect of glyphosate to be visually monitored, whereas, the water content and shikimate data were analyzed with trend analysis and by looking at the significance between variables (ANOVA and Tukey's Comparison, SAS 8.02). Over a I5-day period, the stem tissue showed lethal effects as the water content decreased, suggesting the loss of membrane integrity; shikimate levels rose, suggesting that the critical shikimic enzyme EPSP synthase was blocked; and the fluorescence decreased, suggesting that cell metabolism had ceased. Taken together these results lead toward the conclusion that glyphosate's effect on Amur honeysuckle was lethal to the stem tissue at this point in time.