Seagrasses are often considered "winners" of ocean acidification (OA); however, seagrass productivity responses to OA could be limited by nitrogen availability, since nitrogen-derived metabolites are required for carbon assimilation. We tested nitrogen uptake and assimilation, photosynthesis, growth, and carbon allocation responses of the tropical seagrasses Halodule uninervis and Thalassia hem...

Root nitrate uptake is well known to adjust to the plant's nitrogen demand for growth. Long-distance transport and/or root storage pools are thought to provide negative feedback signals regulating root uptake. We have characterized a vascular specific nitrate transporter belonging to the high-affinity Nitrate Transporter2 (NRT2) family, OsNRT2.3a, in rice (Oryza sativa ssp. japonica 'Nipponbare...

Constructed wetlands could be components of low-tech systems to treat and reuse wastewater in arid region. A key function of the wetland would be to provide additional N removal. To improve design criteria, a sequential model of nitrogen transformations (organic N! ammonium; ammonium!nitrate; nitrate!nitrogen gas) was successfully calibrated and verified for a wetland in Kingman, Arizona. A seq...

1. Riparian zones function as important ecotones that reduce nitrate concentration in groundwater and inputs into streams. In the boreal forest of interior Alaska, permafrost confines subsurface flow through the riparian zone to shallow organic horizons, where plant uptake of nitrate and denitrification are typically high. 2. In this study, riparian zone nitrogen retention was examined in a hig...

Subsidence of the Everglades Histosols occurs at a rate of approximately 3 cm/year. The major cause of this loss of soil is the oxidation of the organic matter by the microbial community. One of the products of this microbial activity is inorganic nitrogen. Assuming an annual subsidence rate of 3 cm, approximately 1400 kg/ha of nitrogen is released per year. Much of this nitrogen accumulates in...

The streams of North America convey excessive amounts of nitrate-nitrogen, the effects of which range from eutrophication of local surface waters to hypoxia in the Gulf of Mexico. The vast majority of the nitrate load can be attributed to agricultural sources. The diffuse nature of these sources defies the more traditional treatment strategies. The concrete and steel structures of point-source ...

Nitrate contamination in rivers has raised widespread concern in the world, particularly in arid/semi-arid river basins lacking qualified water. Understanding the nitrate pollution levels and sources is critical to control the nitrogen input and promote a more sustainable water management in those basins. Water samples were collected from a typical semi-arid river basin, the Weihe River watersh...

Artichoke has a high nitrogen requirements and often farmers apply excessive amounts of fertiliser that contributes to groundwater pollution by nitrate. Artichoke nitrogen fertilisation can be made more efficient by plant analysis. Petiole sap nitrate concentrations in recently mature leaves was tested as an indicator of crop nitrogen status in artichoke grown in sand culture. Two rapid methods...