AbstractMicrosporogenesis of different, temperature‐ and tetracycline‐sensitive cms plants, and male fertile genotypes was investigated.The microsporogenesis of cms plants [(S)xx] and fertile plants [(N)xx or (S)X.]is similar up to the tetrade stage. During the tetrade stage, microspores of cms plants start to die off. The effect of the (S)‐cytoplasm on microsporogenesis is overcome by the restorer gene X, the temperature gene T and by tetracycline gene a. Whereas the X gene acts independently of environmental conditions, the gene T is expressed at constantly high temperature of 24 °C, and the tetracycline gene a acts after tetracycline treatment. After temperature‐ and tetracycline treatment, respectively, the sensitive genotypes need 10—14 days to change from male sterile into male fertile. This period seems to be most interesting to study the influence of the defined nuclear genes on mitochondrial transcription and t