Abstract: To compare two different forms (cDNA in monocotyledonous plants Echinochloa, DNA in monocotyledon Zea mays) of phosphoenolpyruvate carboxylase (PEPC) gene (Ppc) on transformed dicotyledonous plant growth, the Ppc genes were Agrobactirium-transfected into dicotyledon tobacco. Transformed leaf discs and differentiated seedling leaves were verified with GUS histochemistry, PCR, and RT-PCR. It was found that tobaccos transformed with barnyardgrass cDNA grew better than the complete maize DNA Ppc gene. The latter tobacco plants showed lower regeneration efficiency, leaves turned yellow and appeared wilted, possibly due to abnormal chloroplasts, or the complete maize Ppc gene was not expressed correctly in tobacco due to incorrect transcription initiation or incorrect splicing. Therefore to transfer DNA gene between genetically-distant species lower normal expression rate. Net photosynthetic rate (Pn) of transgenic tobacco plants transformed with barnyardgrass cDNA was higher than in untransformed tobacco, indicating that over-expressing Echinochloa root-Ppc gene improved tobacco photosynthesis.