Root adaptation and nitrogen source acquisition in natural ecosystems

Turnbull, M. H., Schmidt, S., Erskine, P. D., Richards, S. and Stewart, G. R. (1996). Root adaptation and nitrogen source acquisition in natural ecosystems. In: International Symposium on Dynamics of Physiological Processes in Woody Roots, Ithaca, NY, United States, (941-948). 8-11 October 1995.

Author Turnbull, M. H.
Schmidt, S.
Erskine, P. D.
Richards, S.
Stewart, G. R.
Title of paper Root adaptation and nitrogen source acquisition in natural ecosystems
Conference name International Symposium on Dynamics of Physiological Processes in Woody Roots
Conference location Ithaca, NY, United States
Conference dates 8-11 October 1995
Journal name Tree Physiology   Check publisher's open access policy
Place of Publication Oxford, United Kingdom
Publisher Oxford University Press
Publication Year 1996
Sub-type Fully published paper
Open Access Status Not Open Access
ISSN 0829-318X
Volume 16
Issue 11-12
Start page 941
End page 948
Total pages 8
Language eng
Formatted Abstract/Summary
The capacity for nitrate reduction, as measured by nitrate reductase activity (NRA), was generally low for a range of plant communities in Australia (coastal heathland, rainforest, savanna woodland, monsoon forest, mangrove, open Eucalyptus forest, coral cay open forest) and only a loose relationship existed between NRA and leaf nitrogen concentration. This suggests that nitrate ions are not the sole nitrogen source in these communities. Based on 15N labeling experiments, we found a range of tree species exhibiting a pronounced preference for uptake of ammonium over nitrate. Analysis of soil solutions from several forest and heathland communities indicated that ammonium ions were more prevalent than nitrate ions and that soluble forms of organic nitrogen (amino acids and protein) were present in concentrations similar to those of mineral nitrogen. To determine the extent to which root adaptations and associations might broaden nitrogen source utilization to include organic nitrogen, we assessed the effects of various nitrogen sources on seedling growth in sterile culture. Non-mycorrhizal seedlings of Eucalyptus grandis W. Hill ex Maiden. and Eucalyptus maculata Hook. grew well on mineral sources of nitrogen, but did not grow on organic sources of nitrogen other than glutamine. Mycorrhizal seedlings grew well on a range of organic nitrogen sources. When offered a mixture of inorganic and organic nitrogen sources at low concentrations, mycorrhizal seedlings derived a significant proportion of their nitrogen budget from organic sources. We also demonstrated that a species of the obligately non-mycorrhizal genus Hakea, a heathland proteaceous shrub possessing cluster roots, had the ability to incorporate 15N-labeled organic sources (e.g., glycine). We conclude that mycorrhizal associations and root adaptations confer the ability to substantially broaden the nitrogen source base on some plant species.
Keyword Ammonium
Cluster root
Nitrate reductase
Q-Index Code E1
Q-Index Status Provisional Code
Institutional Status UQ

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