Chloroplast development in 4-thiouridine-cultured radish seedlings IV. Properties of cellular organelles

The effect of 4-thiouridine (4SU) on metabolic activities oforganelles other than plastids was investigated by examininggrowth parameters, cellular enzyme activities and metabolicbehaviors of greening radish seedlings germinated and grownwith 4SU. Seedling growth was not severely affected by 4SU culture.Mitochondrial, peroxisomal and microsomal marker enzymes andcytoplasmic enzyme activities were not generally changed inthe 4SU-cultured radish cotyledons. The respiration rate ofmitochondria isolated from 4SU-cultured cotyledons was alsonormal. Some soluble enzymes of the isolated plastids had normalor even higher activities. However, chloroplastic pigments andribulose bisphosphate carboxylase activity decreased with increasingconcentration of 4SU in the culture medium. We concluded thatthe inhibitory effect of 4SU was limited to chloroplast development. (Received December 4, 1979; )