caa a22 4500 477109942 CHVBK 20180405111605.0 cr unu---uuuuu 170330e19960401xx s 000 0 eng 10.1007/BF00011299 doi (NATIONALLICENCE)springer-10.1007/BF00011299 Schenk M. Institute of Plant Nutrition, University of Hannover, Herrenhäuser Str. 2, D-30419, Hannover, Germany aut Regulation of nitrogen uptake on the whole plant level [Elektronische Daten] [M. Schenk] The largest part of nitrogen requirements of crops is mostly covered by nitrate. The uptake of this ion is thermodynamically uphill and thus dependent on metabolism. This article considers regulation of N uptake in higher plants putting emphasis on NO3 - and the whole plant level. In field conditions the transport rate depends on the concentration at the root surface in Michaelis-Menten-Kinetics. Maximum net influx of NO3 - (Imax) was often reported at concentrations of 100 μM NO3 - and even lower. There are indications that for unrestricted growth the NO3 - concentration at root surface has to be in the order of magnitude allowing Imax if plants are not able to compensate for lower NO3 - concentrations by increasing root surface per unit of shoot. Imax is not a constant but depends for a given variety on N status of plants, the availability of NO3 - and plant age. The decrease of Imax with increasing plant age is closely related to relative growth rate as long as the relationship between N demand and new growth is linear and the root:shoot ratio keeps constant. It seems that Imax is a meaningful physiological characteristic of NO3 - uptake reflecting absolute N demand. There is evidence that shoot demand is linked to NO3 - uptake of the root through an amino acid transport pool cycling in the plant via phloem and xylem. The N demand of a crop depends on increase of dry mass and might not be linear if the "critical level” of nitrogen in plant dry matter changes during crop development or if retranslocation of nitrogen from older leaves to meristematic tissue occurs. Radiation and temperature drive plant growth and thus N demand of crops. These relationships can be described by mathematical models. Kluwer Academic Publishers, 1996 cucumber nationallicence growth rate nationallicence lettuce nationallicence maximum inflow (Imax) nationallicence model nationallicence nitrate nationallicence regulation nationallicence uptake nationallicence Plant and Soil Kluwer Academic Publishers; gopher://gopher.wkap.nl 181/1(1996-04-01), 131-137 0032-079X 181:1<131 1996 181 11104 https://doi.org/10.1007/BF00011299 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00011299 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Schenk M. Institute of Plant Nutrition, University of Hannover, Herrenhäuser Str. 2, D-30419, Hannover, Germany aut NATIONALLICENCE 773 0- Plant and Soil Kluwer Academic Publishers; gopher://gopher.wkap.nl/ 181/1(1996-04-01), 131-137 0032-079X 181:1<131 1996 181 11104 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer