Details

Autor(en) / Beteiligte

• Fredeen, A.L
• Field, C.B

Titel

Ammonium and nitrate uptake in gap, generalist and understory species of the genus Piper

Ist Teil von

• Oecologia, 1992-11, Vol.92 (2), p.207-214

Ort / Verlag

Berlin: Springer-Verlag

Erscheinungsjahr

1992

Quelle

SpringerLINK Contemporary (Konsortium Baden-Württemberg)

Beschreibungen/Notizen

• We studied root net uptake of ammonium (NH4 +) and nitrate (NO3 -) 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 NH4 +and NO3 -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 NH4 +and/or 100 μM NO3 -) at intermediate PFD (100 μmol m-2s-1). Preference for NH4 +relative to NO3 -, defined as the ratio of NH4 +(both): NO3 -(both) net uptake, was higher in understory species than in gap species. Ammonium repression of NO3 -uptake, defined as the ratio of NO3 -(single): NO3 -(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 NH4 +preference and NH4 +repression of NO3 -net uptake at high (500 μmol m-2s-1) and low (50 μmol m-2s-1) PFD in a gap (P. auritum), generalist (P. hispidum) and understory species (P. aequale). All species exhibited negligible NH4 +repression of NO3 -net uptake at high PFD. At low PFD, NH4 +preference and repression of NO3 -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 NO3 -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 NO3 -or NH4 +net uptake were observed.