comparative study of fluxes and compartmentation of nitrate and ammonium in early-successional tree species

• Published in: Plant, cell and environment cell and environment, 1999-07, Vol.22 (7), p.821-830
• Main Authors: Min, X, Yaeesh Siddiqi, M, Guy, R.D, Glass, A.D.M, Kronzucker, H.J
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; ammonium compounds; ammonium fluxes; Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; compartmental analysis; cytoplasm; cytoplasmic ammonium; cytoplasmic nitrate; Douglas‐fir; Economic plant physiology; Fundamental and applied biological sciences. Psychology; lodgepole pine; nitrate fluxes; nitrates; nitrogen metabolism; Nitrogen metabolism and other ones (excepting carbon metabolism); nitrogen nutrition; nutrient intake; nutrient solutions; nutrient sources; nutrient transport; nutrient uptake; Nutrition. Photosynthesis. Respiration. Metabolism; nutritional status; Pinus contorta; pioneer species; Plants and fungi; Populus tremuloides; Pseudotsuga menziesii; roots; seedlings; shoots; species differences; trembling aspen
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1046/j.1365-3040.1999.00450.x

¹³NO₃⁻ and ¹³NH₄⁺ compartmental analyses were carried out in seedling roots of trembling aspen (Populus tremuloides Michx.), lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) and interior Douglas-fir (Pseudotsuga menziesii var. glauca [Beissn.] Franco) at 0·1 and 1·5 mol m⁻³ external NO₃⁻ or NH₄⁺ concentrations ([NO₃⁻]o or [NH₄⁺]o, respectively). At the lower [NO₃⁻]o, the capacities and efficiencies of acquisition and accumulation of NO₃⁻, based upon NO₃⁻ fluxes and cytoplasmic NO₃⁻ concentrations ([NO₃⁻]c), were in the order aspen >> Douglas-fir > pine. At 1·5 mol m⁻³[NO₃⁻]o, the NO₃⁻ influx increased 18-fold in pine, four-fold in Douglas-fir and approximately 1·4-fold in aspen; in fact, at 1·5 mol m⁻³[NO₃⁻]o, the NO₃⁻ influx in pine was higher than in aspen. However, at high [NO₃⁻]o, efflux also increased in the two conifers to a much greater extent than in aspen. In aspen, at both [NO₃⁻]o, approximately 30% of the ¹³N absorbed was translocated to the shoot during 57 min of ¹³N loading and elution, compared with less than 10% in the conifers. At 0·1 mol m⁻³[NH₄⁺]o, influx and net flux were in the order: aspen > pine > Douglas-fir but the differences were much less than in NO₃⁻ fluxes. At 1·5 mol m⁻³[NH₄⁺]o, NH₄⁺ influx, efflux and [NH₄⁺]c greatly increased in aspen and Douglas-fir and, to a much lesser extent, in pine. In aspen, 29 and 12% of the ¹³N absorbed was translocated to the shoot at 0·1 and 1·5 mol m⁻³[NH₄⁺]o, respectively, compared with 5 to 7% in the conifers at either [NH₄⁺]o. These patterns of nitrogen (N) uptake, particularly in the case of NO₃⁻, and the observed concentration responses of NO₃⁻ uptake, reflect the availability of N in the ecological niches, to which these species are adapted.