1)The permeability of the tissue which surround the venenate zone of Helminthosporium disease ledion of rice leaf, is lower than that of the other healthy part. 2)The lesion size of this disease increased both in the case that the rice leaves treated with ether vapor and that permeated with NH_4NO_3(0.01 M), while the permeability of rice leaves decreased in the former and increased in the latter.