caa a22 4500 469096330 CHVBK 20180323133032.0 cr unu---uuuuu 170328e19921101xx s 000 0 eng 10.1007/BF00317366 doi (NATIONALLICENCE)springer-10.1007/BF00317366 Ammonium and nitrate uptake in gap, generalist and understory species of the genus Piper [Elektronische Daten] [Arthur Fredeen, Christopher Field] Summary: We studied root net uptake of ammonium (NH 4 + ) and nitrate (NO 3 − ) in species of the genus Piper (Piperaceae) under high, intermediate and low photosynthetically active photon flux densities (PFD). Plants were grown hydroponically, and then transferred to temperature controlled (25° C) root cuvettes for nutrient uptake determinations. Uptake solutions provided NH 4 + and NO 3 − simultaneously (both) or separately (single). In the first experiment, seven species of Piper, from a broad range of rainforest light habitats ranging from gap to understory, were screened for mineral nitrogen preference (100 μM NH 4 + and/or 100 μM NO 3 − ) at intermediate PFD (100 μmol m−2 s−1). Preference for NH 4 + relative to NO 3 − , defined as the ratio of NH 4 + (both):NO 3 − (both) net uptake, was higher in understory species than in gap species. Ammonium repression of NO 3 − uptake, defined as the ratio of NO 3 − (single): NO 3 − (both) net uptake, was also higher in understory species as compared to gap species. In a second set of experiments, we examined the effect of nitrogen concentration (equimolar, 10 to 1000 μM) on NH 4 + preference and NH 4 + repression of NO 3 − net uptake at high (500 μmol m−2 s−1) and low (50 μmol m−2 s−1) PFD in a gap (P. auritum), generalist (P. hispidum) and understory species (P. aequale). All species exhibited negligible NH 4 + repression of NO 3 − net uptake at high PFD. At low PFD, NH 4 + preference and repression of NO 3 − net uptake occurred in all species (understory > generalist > gap), but only at intermediate nitrogen concentrations, i.e. between 10 and 200 μM. Ammonium repression of net NO 3 − uptake decreased or increased rapidly (in < 48 h) after transitions from low to high or from high to low PFD respectively. No significant diurnal patterns in NO 3 − or NH 4 + net uptake were observed. Springer-Verlag, 1992 Ammonium uptake nationallicence Neotropics nationallicence Nitrate reductase nationallicence Nitrate uptake nationallicence Piper nationallicence Fredeen Arthur Department of Plant Biology, Carnegie Institution of Washington, 290 Panama Street, 94305, Stanford, CA, USA aut Field Christopher Department of Plant Biology, Carnegie Institution of Washington, 290 Panama Street, 94305, Stanford, CA, USA aut Oecologia Springer-Verlag 92/2(1992-11-01), 207-214 0029-8549 92:2<207 1992 92 442 https://doi.org/10.1007/BF00317366 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00317366 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Fredeen Arthur Department of Plant Biology, Carnegie Institution of Washington, 290 Panama Street, 94305, Stanford, CA, USA aut NATIONALLICENCE 700 1- Field Christopher Department of Plant Biology, Carnegie Institution of Washington, 290 Panama Street, 94305, Stanford, CA, USA aut NATIONALLICENCE 773 0- Oecologia Springer-Verlag 92/2(1992-11-01), 207-214 0029-8549 92:2<207 1992 92 442 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer