The ability of amino compounds and conditioned medium to alleviate the reduced nitrogen requirement of soybean cells grown in suspension cultures

Summary Various nitrogen compounds were tested for their ability to alleviate the reduced nitrogen requirement of soybean cells growing in defined liquid medium containing nitrate as the alternative nitrogen source. Either l-glutamine, l-alanine, putrescine or NH₄ ⁺ satisfied this requirement. Addition of l-glutamate resulted in poor growth. Where growth was stimulated, nitrate reductase (NR) activity increased whereas glutamate dehydrogenase activity in the cells showed no such correlation. In all fresh media which supported rapid growth, NR activity first decreased rapidly to a low value. Subsequent dry weight increases occurred concommitantly with an increase in NR activity. When 2,4-dichlorophenoxyacetic acid was omitted from the medium the growth was slow and the NR activity did not increase. During the first 40 h of incubation in medium containing NH₄ ⁺ plus NO₃ ^- the cells produced a growth-enhancing factor(s). This factor(s) was present in the cells and in the medium and eliminated the requirement for reduced nitrogen.This work was supported by a grant in aid of research from the National Research Council of Canada to one of us (J. K.). NRCC No. 12520