Abstract: In a method for ascertaining phyto-specific characteristics for differently grown crops to differentiate between crop plants that have been subjected to different methods of growing, the following plant parametersFG.sub.max =maximum fresh weight,TG=dry weightAcP=proportion by weight of cell components capable of swellingAH.sub.2 O=proportion by weight of adsorptive waterWH.sub.2 O=proportion of cell water by weightare ascertained and are related to each other in the form of a ratio relativizing locality-dependent modifications. In accordance with a second form of the invention an enzyme, such as glutamate dehydrogenase, or an enzyme mixture present in the plants to be investigated and reacting particularly sensitively to an alteration in the supply of nitrogen, is isolated and the relaxation time .tau. of the enzyme is ascertained for different enzyme concentrations.