|PEZESHKI, S. REZA|
Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/28/2008
Publication Date: 9/10/2009
Citation: Pierce, S.C., Pezeshki, S.R., Moore, M.T., Larsen, D. 2009. Nutrient response of Bacopa monnieri (water hyssop) to varying degrees of soil saturation. Journal of Plant Nutrition. 32:1687-1701.
Interpretive Summary: Vegetation in wetlands and other conveyance habitats can act as filters for contaminants associated with water. Little is known about the impacts of physiological plant stress on vegetation’s ability to sorb nutrients and other potential contaminants. This study was designed to characterize responses of an aquatic plant common in marshes in the Gulf of Mexico to soil moisture contents ranging from well-drained to saturated. Decreases in plant nitrogen uptake were noted as flooding times increased. These results, suggesting decreased mineral transport, have significant implications as to what type of plants would be most efficient in pollution remediation systems such as constructed wetlands.
Technical Abstract: Tissue concentrations of N and P were measured in Bacopa monnieri subjected to four progressive levels of flooding: well-drained Control, Intermittently Flooded, Partially Flooded, and Continuously Flooded. Soil redox potential (Eh) decreased in all flooded treatments at 30 cm depth, becoming anoxic by day 30, while at 10 cm Eh was more variable than 30 cm. The resulting soil anoxia was implicated in decreased root growth and plant N and P uptake, with these effects being most pronounced in the Partially Flooded and Continuously Flooded treatments. Flood-related decreases in N uptake were likely the result of plant stress and the reduction in available nitrogen in NO3- form to the less preferred NH4+. Decreases in plant P concentrations may have been unrelated to chemical species of P, and were more likely the result of decreased root growth limiting the soil:plant interface. The decreased uptake of N and P under flooding underscores the need to better understand how wetland plants function in nutrient rich environments subjected to variable flooding. Additionally, the apparent decreased translocation of N and P from the root to the shoot in flooding conditions may be representative of an overall decrease in mineral transport, which would have implications for the design and management of remediation systems.