The Partitioning of Nitrate Assimilation Between Root and Shoot of a Range of Temperate Cereals and Pasture Grasses
1992
Andrews, M. | Morton, J.D. | Lieffering, M. | Bisset, L.
Nitrate reductase activity (NRA, in vivo assay) and nitrate (NO3(-1)) content of root and shoot and NO3(-1) and reduced nitrogen content of xylem sap were measured in five temperate cereals supplied with a range of NO3(-1) concentrations (0.1-20 mol m-3) and three temperate pasture grasses supplied with 0.5 or 5.0 mol m-3 NO3(-1). For one cereal (Hordeum vulgare L.), in vitro NRA was also determined. The effect of external NO3(-1) concentration on the partitioning of NO3(-1) assimilation between root and shoot was assessed. All measurements indicated that the root was the major site of NO3(-1) assimilation in Avena sativa L., Hordeum vulgare L., Secale cereale L., Triticum aestivum L. and X Triticosecale Wittm. supplied with 0.1 to 1.0 mol m-3 NO3(-1) and that for all cereals, shoot assimilation increased in importance as applied NO3(-1) concentration increased from 1.0 to 20 mol m-3. At 5.0-20 mol m-3 NO3(-1), the data indicated that the shoot played an important if not major role in NO3(-1) assimilation in all cereals studied. Measurements on Lolium multiflorum Lam. and L. perenne L. indicated that the root was the main site of NO3(-1) assimilation at 0.5 mol m-3 NO3(-1) but shoot assimilation was predominant at 5.0 mol m-3 NO3(-1). Both NRA distribution data and xylem sap analysis indicated that shoot assimilation was predominant in Dactylis glomerata L. supplied with 0.5 or 5.0 mol m-3 NO3(-1).
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