TY - JOUR
T1 - Outstanding Lobelia dortmanna in iron armor
AU - Jensen, Kaj Sand
AU - Møller, Claus Lindskov
AU - Raun, Ane-Marie Løvendahl
N1 - Keywords:Isoetids, Lobelia dortmanna, iron ROL,
sediment oxygen, iron plaques
PY - 2008
Y1 - 2008
N2 - Lobelia dortmanna leads a group of small, highly-valued rosette species that grow on coarse, nutrient-poor soils in temperate softwater lakes. They acquire most CO2 for photosynthesis by root uptake and efficient gas transport in large air channels to the leaves. Lobelia is the only species that releases virtually all photosynthetic oxygen from the roots and generates profound day-night changes in oxygen and CO2 in the sediment pore-water. While oxygen release from roots stimulates decomposition and supports VA-mycorrhiza fungi, the ready gas exchange presents a risk of insufficient oxygen supply to the distal root meristems as sediments accumulate organic matter from lake pollution. So the plant with the greatest oxygen release from roots is also the most sensitive to oxygen depletion in sediments and it dies or losses anchorage by shortening the roots from 10 to 2 cm at even modest contents (2.4%) of degradable organic matter. Coatings of oxidized iron on roots in organically enriched sediments reduce radial oxygen loss and, thereby, increase internal concentrations and supply of oxygen to root tips. Oxidized iron is also a redox buffers which may prevent the ingress of sulfides and other reduced toxic solutes during nights. Controlled experiments are under way to test if iron enrichment can help survival of rosette species threatened by lake pollution or whether removal of organic surface sediments is required.
AB - Lobelia dortmanna leads a group of small, highly-valued rosette species that grow on coarse, nutrient-poor soils in temperate softwater lakes. They acquire most CO2 for photosynthesis by root uptake and efficient gas transport in large air channels to the leaves. Lobelia is the only species that releases virtually all photosynthetic oxygen from the roots and generates profound day-night changes in oxygen and CO2 in the sediment pore-water. While oxygen release from roots stimulates decomposition and supports VA-mycorrhiza fungi, the ready gas exchange presents a risk of insufficient oxygen supply to the distal root meristems as sediments accumulate organic matter from lake pollution. So the plant with the greatest oxygen release from roots is also the most sensitive to oxygen depletion in sediments and it dies or losses anchorage by shortening the roots from 10 to 2 cm at even modest contents (2.4%) of degradable organic matter. Coatings of oxidized iron on roots in organically enriched sediments reduce radial oxygen loss and, thereby, increase internal concentrations and supply of oxygen to root tips. Oxidized iron is also a redox buffers which may prevent the ingress of sulfides and other reduced toxic solutes during nights. Controlled experiments are under way to test if iron enrichment can help survival of rosette species threatened by lake pollution or whether removal of organic surface sediments is required.
M3 - Journal article
SN - 1559-2316
VL - 3
SP - 882
EP - 884
JO - Plant Signalling & Behavior
JF - Plant Signalling & Behavior
IS - 10
ER -