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Nitrogen-Utilization by Plant-Species from Acid Heathland Soils .1. Comparison between Nitrate and Ammonium Nutrition at Constant Low Ph

Troelstra, S.R. and Wagenaar, R. and Smant, W. (1995) Nitrogen-Utilization by Plant-Species from Acid Heathland Soils .1. Comparison between Nitrate and Ammonium Nutrition at Constant Low Ph. Journal of Experimental Botany, 46, 1103-1112. ISSN 0022-0957.

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Official URL: http://dx.doi.org/10.1093/jxb/46.9.1103

Abstract

Seven heathland species, four herbaceous plants and three dwarf shrubs, were tested for their capacity to utilize NH4+ or NO3-. When cultured in solution at pH 4.0 with 2 mol m(-3) N, all species showed similar growth responses with respect to N source. Nitrate was assimilated almost equally well as ammonium, with relative growth rate generally averaging 5-8% lower for NO3- grown plants, albeit not always significantly, However, N source was significantly and consistently correlated with biomass partitioning, as NH4+-fed plants allocated more dry matter to shoots and less to roots when compared to NO3-- fed plants, The strong difference in biomass partitioning may relate to the relative surplus of carbon per unit plant N (or, alternatively, the relatively suboptimal rate of N assimilation per unit plant C) in NO3--fed plants. Inherently slow-growing dwarf shrubs accumulated virtually no free nitrate in their tissues and reduction of nitrate was strictly root-based, Faster-growing herbaceous plants, however, partitioned the assimilation of nitrate over both shoots and roots, thereby accumulating relatively high tissue NO3--levels. ion uptake rates depended clearly on the 'relative shoot demand', At similar shoot demands, especially in the herbaceous species, specific uptake rates for N and total inorganic (non-N) anions were higher in NH4+-fed plants, whereas the uptake rate for total (non-N) cations was higher in NO3--fed plants, Rate of P uptake was enhanced with increasing plant demand, but was independent of the N source, Net H+ extrusions ranged from 1.00 to 1.34 H+ per NH4+, and from -0.48 to -0.77 H+ per NO3- taken up. [KEYWORDS: Ammonium; biomass partitioning; heathland plants; low ph; nitrate; nitrate reductase activity; relative shoot demand; specific absorption rate Zea-mays l; chemical-composition; functional equilibrium; ricinus-communis; vascular plants; lolium-perenne; root-zone; growth; form; absorption]

Item Type:Article
Institutes:Nederlands Instituut voor Ecologie (NIOO)
ID Code:12217
Deposited On:25 Nov 2011 01:00
Last Modified:15 Jan 2014 09:39

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