RESUMO
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 cultures. The conditioned media of crops did not activate the growth of a diluted (400-fold) culture of tobacco cells. Conditioned media from the cultures of cells of other monocotyledonous plants, such as asparagus or spiderwort, stimulated the tobacco culture growth like those from the cultures of cells of dicotyledonous and gymnospermous plants. The growth of a diluted (2000-fold) culture of wheat cells was activated by the conditioned media from all cell cultures used in these experiments. We can propose that conditioning factors of monocotyledonous, dicotyledonous and gymnospermous plants do not differ from each other in the character of biological action and may have a similar chemical nature. The nil or weak activity of conditioned media from the cultures of crop cells may be related to the presence, in addition to the conditioning factors, of inhibitors of cell culture growth.
