Simultaneous measurement of ammonium, nitrate and proton fluxes along the length of eucalypt roots
Date
2001
Authors
Garnett, T.
Shabala, S.
Smethurst, P.
Newman, I.
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Journal article
Citation
Plant and Soil: international journal on plant-soil relationships, 2001; 236(1):55-62
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Abstract
Knowledge of the preferred source of N for Eucalyptus nitens will lead to improved fertiliser management practices in plantations. Ion selective microelectrodes were used non-invasively to measure simultaneously net fluxes of NH<inf>4</inf><sup>+</sup>, NO<inf>3</inf><sup>-</sup> and H<sup>+</sup> along the tap root of solution-cultured E. nitens. Measurements were conducted in solutions containing 100 μm NH<inf>4</inf>NO<inf>3</inf>. The pattern of fluxes was such that there was a large influx of NH<inf>4</inf><sup>+</sup> a smaller influx of NO<inf>3</inf><sup>-</sup> and large H<sup>+</sup> efflux. The ratio of these fluxes was constant, according to the ratio 3:1:-6 (NH<inf>4</inf><sup>+</sup>:NO<inf>3</inf><sup>-</sup> :H<sup>+</sup>). Within the region 20-60 mm from the root apex of E. nitens seedlings there was spatial and temporal variation in fluxes but flux patterns remained constant. Root hair density did not affect fluxes nor did proximity to lateral roots. Variation was less than that found in previous studies of localised root fluxes using similar high-resolution measurement techniques. It was concluded that small-scale spatial variation in fluxes may have confounded previous studies. There were associations between fluxes of all three ions, the strongest associations being between NH<inf>4</inf><sup>+</sup> and H<sup>+</sup>, and NH<inf>4</inf><sup>+</sup> and NO<inf>3</inf><sup>-</sup>. Overall, these results are consistent with NH<inf>4</inf><sup>+</sup> being the preferred source N for E. nitens.
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The original publication can be found at www.springerlink.com