Gas transfer in wetland plants controlled by Graham’s law of diffusion

Abstract

In wetland plants, internal transfer of gases is vital for growth on permanently water-saturated or waterlogged soils, being required to supply oxygen to the rhizomes and roots. Over the past decade, various physical mechanisms have been proposed to be responsible for pressurized ventilation in plants which are adapted to wetland and freshwater habitats. It has now become clear that transfer effects that can be described by Graham’s law of diffusion are involved in this process, in addition to thermal transpiration, humidity-induced and venturi-induced gas transport in swamp grasses. Gas flow in accordance with Graham’s law has also been reported for roots of Alnus (alder) trees. We suggest that this effect may contribute significantly to oxygen supply to the rhizosphere and to the remineralization of organic compounds in soil, thus improving plant nutrition.