Comparative Effects of Deicing Agents on Roadside Vegetation in Southern Michigan

Approximately 25 million tons of deicing agents are applied annually to roads in the United States, raising concerns about increasing environmental salinity and its effects on roadside vegetation. Sodium chloride (NaCl), the most widely used deicer due to its low cost and effectiveness, has been shown to disrupt essential plant functions, including root growth, stomatal regulation, photosynthesis, and pigment stability. This study investigated the physiological and growth responses of three common roadside species in southern Michigan, Asclepias syriaca (common milkweed), Rumex hydrolapathum (great water dock), and Helenium autumnale (common sneezeweed), to varying levels of NaCl exposure. Seedlings were grown under greenhouse conditions and treated twice weekly with increasing NaCl solutions. Growth was measured weekly, and photosynthetic performance was assessed using Li-Cor analysis to estimate Vcmax. Leaf tissue from R. hydrolapathum was harvested for pigment analysis. Samples were ground in liquid nitrogen, extracted in acidified methanol, and analyzed using the spectrophotometer to quantify total chlorophyll and anthocyanin concentrations. Results indicated that increasing salinity significantly reduced total chlorophyll content and increased anthocyanin concentration in R. hydrolapathum, with statistically significant differences observed primarily at the highest treatment level (54 mM), suggesting a threshold-dependent stress response. Although mean Vcmax values were lowest in the highest salt treatment, differences among treatment groups were not statistically significant, indicating limited evidence that NaCl altered the plants’ capacity to upregulate Rubisco activity under the conditions tested. Growth responses across treatments were variable and did not show consistent statistically significant trends. These findings support the hypothesis that elevated soil salinity from deicing agents can induce physiological stress in roadside plants, particularly through pigment degradation and increased anthocyanin production. Identifying salinity thresholds that impair chlorophyll production may inform conservation strategies, roadside vegetation management, and the selection of salt-tolerant species in regions affected by winter road maintenance practices.