Influence of plants on redox potential and methane production in water-saturated soil

Abstract

Pressurized ventilation, which increases the oxygen supply of the roots and rhizomes, has been detected on three waterlilies (Nymphaea capensis, N. lotus var. lotus, N. odorata), two Japanese swamp grasses (Ischaemum aristatum var. glaucum, Isachne globosa), and three willow species (Salix alba, S. cinerea, S. viminalis). All of these plant species are able to generate sufficient convective gas flow to meet the oxygen demand of their organs buried in the anoxic soil. Excretion of surplus oxygen maintains higher redox potential in the tussock of I. aristatum and also in the rhizosphere of the waterlilies and willows, thereby protecting the root system from phytotoxin uptake. High methane production rates in reduced sediments contrast to the significantly lower rates of methane formation in the oxidized rhizosphere surrounding N. lotus roots. This is an example of how wetland plants use pressurized ventilation to alter microbial activities in their habitat. Pressurized ventilation seems to provide these plant species with a competetive advantage over species that rely on diffusive aeration of their submerged parts, thereby enabling them to become dominant weeds in their aquatic ecosystems or in wet meadows of nature reserves.