Separate auxin- and cation-dependent mechanisms for glutamate utilization by normal and crown-gall teratoma cells of tobacco in culture.

Crown-gall teratoma tissues of tobacco, when grown in culture, require exogeneous auxin (α-naphthaleneacetic acid) or high concentrations of K(+) in the medium to utilize ammonium glutamate as a nitrogen source. These factors are not required to utilize NO 3 (-) or glutamine. The effects of K(+) and auxin on glutamate utilization differ in that NH 4 (+) is required for the action of K(+), but not for the action of auxin. The tissues grew optimally when the ratio of NH 4 (+) to glutamate was approximately one or greater. These results indicate that glutamate utilization involves at least two different mechanisms: one mechanism requires K(+) and stoichiometric amounts of NH 4 (+) , the other mechanism requires auxin. Experiments using explants of tobacco pith show that both mechanisms function in normal as well as crown-gall tissues of tobacco.