Annals of Botany 89: 435-442, 2002
© 2002 Annals of Botany Company
The Effect of Nitrogen Nutrition on Cluster Root Formation and Proton Extrusion by Lupinus albus
1Soil Science and Plant Nutrition, The University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Australia and 2Research Institute of Pomology and Floriculture, Pomologiczna 18, 96–100 Skierniewice, Poland
* For correspondence. E-mail: lsas{at}insad.pl
Received: 25 June 2001; Returned for revision: 1 November 2001; Accepted: 6 January 2002.
Nitrogen nutrition can influence cluster root formation in many wild species, but the effect of N form on cluster root formation and root exudation by white lupin is not known. In a solution culture study, we examined the effect of N nutrition (ammonium, nitrate, both or N2 fixation) on cluster root formation and H+ extrusion by white lupin plants under deficient and adequate P supply. The number of cluster roots increased greatly when plants were supplied with 1 µM P compared with 50 µM P, the increase being 7·8-fold for plants treated with (NH4)2SO4, 3-fold for plants treated with KNO3 and NH4NO3, and 2·4-fold for N2-fixing plants. Under P deficiency, NH4+-N supply resulted in production of a greater number and biomass of cluster roots than other N sources. Dry weight of cluster roots was 30 % higher than that of non-cluster roots in P-deficient plants treated with (NH4)2SO4 and NH4NO3. In plants treated with sufficient P (50 µM), the weight of non-cluster roots was approx. 90 % greater than that of cluster roots. Both total (µmol per plant h–1) and specific (µmol g–1 root d. wt h–1) H+ extrusions were greatest from roots of plants supplied with (NH4)2SO4, followed by those supplied with NH4NO3 and N2 fixation, whereas plants receiving KNO3 had negative net H+ extrusion between the third and fifth week of growth (indicating uptake of protons or release of OH– ions). The rate of proton extrusion by NH4+-N-fed plants was similar under P-deficient and P-sufficient conditions. In contrast, proton exudation by N2-fixing plants and KNO3-treated plants was ten-fold greater under P deficiency than under P sufficiency. In comparison with P deficiency, plants treated with 50 µM P had a significantly higher concentration of P in roots, shoots and youngest expanded leaves (YEL). Compared with the N2 fixation and KNO3 treatments, total N concentration was highest in roots, shoots and YEL of plants supplied with (NH4)2SO4 and NH4NO3, regardless of P supply. Under P deficiency, K concentrations in roots decreased at all N supplies, especially in plants treated with (NH4)2SO4 and NH4NO3, which coincided with the greatest H+ extrusion at these P and N supplies. In conclusion, NH4-N nutrition stimulated cluster root formation and H+ extrusion by roots of P-deficient white lupin.
Key words: Cluster roots, H+ extrusion, mineral composition, N2 fixation, N nutrition, P deficiency, white lupin.
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  A. de Santiago and A. Delgado Predicting Iron Chlorosis of Lupin in Calcareous Spanish Soils from Iron Extracts Soil Sci. Soc. Am. J., September 20, 2006; 70(6): 1945 - 1950. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. A. Raven, L. L. Handley, and M. Andrews Global aspects of C/N interactions determining plant-environment interactions J. Exp. Bot., January 1, 2004; 55(394): 11 - 25. [Abstract] [Full Text] [PDF]
|
|