The fatty-acid composition of C. roseus and N. tabacum cell suspension cultures was unaffected by subculture on Wood and Braun, Murashige and Skoog, or Gamborg B5C media. However, placing the cultures - which were normally grown at 25° C - at 15° C reduced growth but resulted in enhanced formation of oleic and linolenic acids in C. roseus cultures and increased levels of linoleic and linolenic acids in cultures of G. max and N. tabacum, respectively. The incorporation of [(14)C]acetate into [(14)C]linoleic acid was more rapid in N. tabacum cells than in G. max cells, but was very poor in C. roseus where the [(14)C] label was distributed mainly between palmitic and oleic acids.