The present invention provides novel polynucleotides encoding plant Na.sup.+/H.sup.+ antiporter polypeptides, fragments and homologs thereof. Also provided are vectors, host cells, antibodies, and recombinant methods for producing said polypeptides. The invention further relates to methods of applying these novel plants polypeptides to the identification, prevention, and/or conferment of resistence to various plant diseases and/or disorders, particularly those associated with modulating environmental stress responses, such as drought and salt tolerance.