The composition of a medium is described that proved useful to culture callus of a variety of monocotyledonous and dicotyledonous plants. Growth on the medium was often better than on some other excellent media. In addition to supporting rapid cell growth, a soft, friable type of colony growth was often obtained. This type of loose, friable cell growth facilitated work with single cells and the enzymatic removal of cell walls in related studies. A high level of auxin-type growth-regulating substances (AGRS) generally favored cell cultures of monocotyledonous plants, while low levels of cytokinin were essential for most dicotyledonous cell cultures. Some cultures of dicotyledonous plant cells adapted to a cytokinin-free medium containing a high level of 2,4-dichlorophenoxyacetic acid (2,4-D) orp-chlorophenoxyacetic acid (pCPA). The preferred AGRS were 2,4-D andpCPA. Citrate, succinate, and 2(N-morpholino) ethane sulfonic acid (MES) were effective medium buffers, but phosphate alone seemed adequate to buffer the medium at pH 5.8ndash;5.9.
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