A method is described for the preparation of a tRNA-dependent wheat germ protein-synthesizing system. This system can be supplied with exogenous tRNAs of eukaryotic or prokaryotic origin. In order to obtain maximal aminoacylation of the added tRNAs, the translation assays can be supplemented with homologous aminoacyl-tRNA synthetase preparations. Such a tRNA-dependent wheat germ protein-synthesizing system, which is easy to prepare, can be used not only to translate plant cytoplasmic mRNAs in the presence of added cytoplasmic tRNAs, but also to determine the translation activity of exogenous tRNAs from various sources in the presence of either natural or in vitro synthesized mRNAs.