Full-strength MS is high in
ammonium (20.6 mM) and nitrate ions (39.4 mM), while
QL is a low ammonium medium (5 mM). WPM contains
low concentrations of both ammonium (5 mM) and nitrate
(9.7 mM) ions. In addition, QL uses calcium nitrate as a
nitrogen source. A medium originally developed for walnut
(Driver and Kuniyuki 1984), designated DKW, also has
lower ammonium ion content (17.7 mM) than MS and
contains calcium nitrate instead of potassium nitrate. The
efficacy of DKW for axillary shoot proliferation of pear has
not been assessed