Studies on the Growth in Culture of Plant Cells: X. FURTHER STUDIES ON THE CONDITIONING OF CULTURE MEDIA BY SUSPENSIONS OF ACER PSEUDOPLATANUS L. CELLS

The standard synthetic culture medium (Stuart and Street, 1969)has been modified by adjustment of its initial pH to 6.4 andby the addition of gibberellic acid (0.25 mg/l) and of a mixtureof 15 L-amino acids formulated from an analysis of the conditionedmedium. The minimum effective density for the growth of sycamorecell suspensions in the standard medium is 9–15 x 10³cells ml^–1, for the modified synthetic medium it is 2.0x 10³ cells ml^–1, and for conditioned medium 1.0–1.25x 10³ cells ml^–1. Using either conditioned medium (Stuart and Street, 1969) orthe modified synthetic medium it is demonstrated that the growthof cultures initiated at low density is enhanced by a volatilefactor released from actively growing cell suspensions. In presenceof conditioned medium and this volatile factor cultures canbe established from stationary-phase cells at a density of 6x 10² cells ml^–1. The volatile factor can be absorbedin 40 per cent w/v KOH but attempts to replace the factor byair containing carbon dioxide at concentrations up to 5 percent have so far been unsuccessful.