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

Summary

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.