Nitrification‐denitrification at the plant root‐sediment interface in wetlands

Abstract

Oxygen transport through the air spaces (aerenchyma tissue) of the stem and roots of aquatic macrophytes into the root zone supports nitrification of NH,+, with the NOJ-formed diffusing into the adjacent anaerobic zone where it undergoes #denitrification. To test this hypothesis, we conducted a growth chamber study to determine the transformation of applied 15NH,+-N to r5N, in the root zone of three aquatic macrophytes: rice (Oryza sativa L.), pickerel weed (Pontecferia cordata L.), and soft rush (Juncus e&us L.). Detection of gaseous 15N, in the air above the floodwater of the soil column with aquatic plants provided direct evidence of nitrification-dcnitrification in the root zone, while such losses were not measurable for soil columns without plants. Air spaces in aquatic plants can also function as conduits for denitrified gases from anaerobic sediments to the atmosphere. Maximal 15N, flux due to this process was 102, 113, and 122 mg N m-2 d-l for soft rush, rice, and pickerel weed. This N loss mechanism has important agronomic and ecological consequences.

Role of Plants in a Constructed Wetland: Current and New Perspectives

“…Thomas et al. [68] mentioned that aerenchyma tissue plays a role in the emission of methane into the atmosphere through emergent wetland plants, supporting Reddy et al [69] who revealed the role of aerenchyma in releasing, to the atmosphere, N 2 and N 2 O produced by anaerobic denitrification of NO 3 in the wastewater. Brix [2] suggested that plants in CWs increase wildlife diversity, but we did not find any empirical study showing this effect or explaining this particular function.…”

Nitrification and denitrification in the rhizosphere of the aquatic macrophyte Lobelia dortmanna L.

“…Reddy et al (1989) observed that roots of rice (Oryza sativa) stimulated the coupled nitrificationdenitrification activity in waterlogged soils, and Caffrey and Kemp (1992) observed significant nitrification-denitrification activity in the rhizosphere of Potamogeton per$oliatusvegetated sediments. Christensen and Sorensen (1988) measured high rates of denitrification in the root zone of freshwater macrophyte Litorellu uniflora-vegetated sediments.…”

The Fate of 15 N-Nitrate in Healthy and Declining Phragmites australis Stands

“…Aerenchymatous plants create an oxic-anoxic interface in the root zone by releasing oxygen into this zone [2,22]. The release of oxygen by the roots may stimulate nitrification [5,9,19] and, subsequently, denitrification after diffusion of nitrate into the reduced zone of the sediment. The decline of the aerenchymatous plant Phragmites australis (Cav.)…”