"Conditioning factor" in cultures of plant cells of various taxa

The activity of the "conditioning factor" from the cultures of plant cells of various taxa was assayed in biotests with the tobacco and wheat cell cul tures. The conditioned media of crops did not activate the growth of a dilu ted (400-fold) culture of tobacco cells. Conditioned media from the culture s of cells of other monocotyledonous plants, such as asparagus or spiderwor t, stimulated the tobacco culture growth like those from the cultures of ce lls of dicotyledonous and gymnospermous plants. The growth of a diluted (20 00-fold) culture of wheat cells was activated by the conditioned media from all cell cultures used in these experiments. We can propose that condition ing factors of monocotyledonous, dicotyledonous and gymnospermous plants do not differ from each other in the character of biological action and may h ave a similar chemical nature. The nil or weak activity of conditioned medi a from the cultures of crop cells may be related to the presence, in additi on to the conditioning factors, of inhibitors of cell culture growth.