Suspension cultures ofLactucaandEuphorbiawere grown in three different experimental media. Growth measurements in terms of increase in fresh weight of tissue, and degree of tissue dissociation after 6 weeks in culture was found to be greatest in medium containing yeast extract (1ensp;g/l.), less in medium containing a completely defined synthetic mixture, and least in medium containing coconut milk (15). Quantitative lignin determinations made on tissues growing in the three media showed high lignin values (in mu;g/mg dry weight of tissue sample) in tissue growing in coconut milk medium, less in tissues growing in synthetic mixture, and least in tissues growing in yeast extract medium. The results thus point out that nutritional factors added to culture media influence not only the growth rate of cultures but also the nature of friability of callus tissue, and the degree of lignification of the growing tissue. Potentialities of using suspension cultures to study lignification processes are pointed out.
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