We investigate the possibility of producing biofuel cell electrode materials in vivo by injecting the reagents directly into plant tissues. We first introduce model electroactive substances Fe(CN)(6)(4-) and Ru(NH3)(6)(3+) into a Nicotiana tabacum leaf. In situ electrochemical measurements make it possible to trace the distribution of these substances. As well as mapping the vascular content, electrochemistry can be used to trigger reactions directly inside the plant. The injection of thiophene (T) and ethylenedioxythiophene (E)-based trimers (ETE) anchoring an Os(2,2-bipyridine)(2)(1-(3-aminopropyl)-imidazole)Cl Os-complex followed by the application of anodic polarization triggers a polymerization reaction in the region of the plant vascular system containing the monomer, showing that it is possible to generate electmactive organic macromolecules locally in vivo.