Computing the permanental polynomials of bipartite graphs by Pfaffian orientation

The permanental polynomial of a graph G is π(G,x) , per(xI −A(G)). From the result that a bipartite graph G admits an orientation Ge such that every cycle is oddly oriented if and only if it contains no even subdivision of K2,3, Yan and Zhang showed that the permanental polynomial of such a bipartite graph G can be expressed as the characteristic polynomial of the skew adjacency matrix A(Ge). In this paper we first prove that this equality holds only if the bipartite graph G contains no even subdivision of K2,3. Then we prove that such bipartite graphs are planar. Further we mainly show that a 2-connected bipartite graph contains no even subdivision of K2,3 if and only if it is planar 1-cycle resonant. This implies that each cycle is oddly oriented in any Pfaffian orientation of a 2-connected bipartite graph containing no even subdivision of K2,3. As applications, permanental polynomials for some types of bipartite graphs are computed.