Plant Nitrogen Transport and Its Regulation in Changing Soil Environments

In this chapter, we shall review plant responses to changes in supply of the two inorganic N sources nitrate (NO3-) and ammonium (NH4+), with an emphasis on primary mechanisms of transport, and their regulation. The topics discussed here include: soil N resources and their ecological implications for plant life; parallel responses in plant growth and N transport activity as functions of N supply; transport kinetics; inducibility and downregulation of NO3- and NH4+ acquisition; plant sensing of NO3-; and low-affinity N transport. Throughout, we attempt to identify areas that are controversial, and those in need of further examination. (C) 2005 by The Haworth Press, Inc. All rights reserved.