These are major journals in Plant Science, as seen in the database Journal Citation Reports. See JCR for impact factors.
Journal of Integrative Plant Biology online 47(1) - 2005-
Phytopathology 69(1)- 1979 - in print back to 1911 at LSF
Plant Physiology and Biochemistry online 36(1) - 1998- in print 1987-1988, 1994-1997 at LSF
Plant Science (previous title Plant Science Letters)
Preslia online 1914-1971 selected volumes in print at LSF