Growth inhibition of tobacco tissue cultures with 6-azauracil, 6-azauridine and maleic hydrazide

Tissue cultures of Nicotiana tabacum, Nicotiana suaveolens and Nicotiana suaveolens × Nicotiana langsdorffii were cultured in the presence of the growth inhibitors maleic hydrazide and 6-azauracil as well as 6-azauridine. Inhibition of growth was complete at 10⁻⁴ molar concentrations in all 3 genotypes of cells. The inhibition due to 6-azauracil could be completely relieved with uridine and partially relieved with uracil. The effect with maleic hydrazide was irreversible, a fact which indicates a different mechanism or level of inhibition. This study supports the concept that derivatives of 6-azauracil inhibit the synthesis of uridine derivatives required for ribose nucleic acid synthesis and growth.