The plant microbial fuel cell (PMFC) is a technology for the production of renewable and clean bioenergy based on photosynthesis. To increase the power output of the PMFC, the internal resistance (IR) must be reduced. The objective of the present study was to reduce the membrane resistance by changing the transport direction of cations in the direction of the established concentration gradient. Two setups, a MFC and PMFC, were designed with one anode and two cathode compartments to demonstrate the effect of changing the transport direction. This design allowed changing the direction of transport of cations by switching the cathode compartment that functions as cathode. The change between cathode 1 and cathode 2 enhanced the power output of the PMFC by 398%. More specifically, after changing transport direction, the increase in power output was due to the reduction of IR (normalized to membrane area) from 4.3 m2mem to 1.2 m2mem in the PMFC. Consecutive changes of cathodes resulted in an increase of generated power with cathode 1 while this power decreased for cathode 2. During the consecutive changes, the average power output remained constant 0.0362 +/- 0.0005 W m-2mem; this was 246% higher than the initial power output with cathode 1. Copyright (c) 2012 John Wiley & Sons, Ltd.