METHANE FLUX IN PELTANDRA-VIRGINICA (ARACEAE) WETLANDS - COMPARISON OF FIELD DATA WITH A MATHEMATICAL-MODEL

We present a mathematical model of the diffusive flux of methane through Peltandra virginica. Data on the diurnal changes in both the petiolar [CH4] gradient and the values of the radial bulk exchange coefficient, E(r), are entirely consistent with this model and the assertion that changes in stomatal conductance regulate the rate of methane efflux in P. virginica. The differences between the values of E(r) calculated for daytime and nighttime conditions are -40% for the submerged condition and -54% for the emergent condition. The axial diffusivity of CH4 through the petiole of P. virginica is estimated in vitro to be 0.771 cm(2) min(-1). Using our model, we estimate the equilibrium rate of methane efflux under daytime (97 ng CH4 min(-1) petiole(-1)) and nighttime (65 ng CH4 min(-1) petiole(-1)) emergent conditions. Numerical solutions of the model equations in the time domain offer a way of providing a dynamic model of the gas exchange responses of P. virginica to changing environmental conditions.