INFLUENCE OF PLANTS ON REDOX POTENTIAL AND METHANE PRODUCTION IN WATER-SATURATED SOIL

Pressurized ventilation, which increases the oxygen supply of the root s and rhizomes, has been detected on three waterlilies (Nymphaea capen sis, N. lotus var. lotus, N. odorata), two Japanese swamp grasses (Isc haemum aristatum var. glaucum, Isachne globosa), and three willow spec ies (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 surplu s oxygen maintains higher redox potential in the tussock of I. aristat um and also in the rhizosphere of the waterlilies and willows, thereby protecting the root system from phytotoxin uptake. High methane produ ction rates in reduced sediments contrast to the significantly lower r ates of methane formation in the oxidized rhizosphere surrounding N. l otus roots. This is an example of how wetland plants use pressurized v entilation to alter microbial activities in their habitat. Pressurized ventilation seems to provide these plant species with a competetive a dvantage over species that rely on diffusive aeration of their submerg ed parts, thereby enabling them to become dominant weeds in their aqua tic ecosystems or in wet meadows of nature reserves.