Kinetin, benzyladenine, isopentenyladenine, and zeatin
broke dormancy of dehulled red rice at 5 x 10-4 to 10-3 M
(Figure 1). Germination was as high as 90% at 10-3 M. Zeatin,
however, was less active than the other cytokinins. The response
to cytokinins was probably not a non-specific substrate
or osmotic effect because adenine at concentrations
as high as 10-2 M failed to stimulate germination. A similar
lack of response to adenine has been observed with lettuce
seeds (14). Intact seeds did not respond to cytokinins at
any of the concentrations tested. Intact cultivated rice is
also insensitive to kinetin (17).