These are major journals in Plant Science, as seen in the database Journal Citation Reports. See JCR for impact factors.
Annual Review of Plant Biology
Annual Review of Phytopathology
Critical Reviews in Plant Sciences
Current Opinion in Plant Biology
Journal of Experimental Botany
Journal of Integrative Plant Biology online 47(1) - 2005-
Molecular Plant-Microbe Interactions
Perspectives in Plant Ecology, Evolution, and Systematics
Phytopathology 69(1)- 1979 - in print back to 1911 at LSF
Plant Cell Tissue and Organ Culture
Plant Molecular Biology Reporter
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