Effect of humic substances on in vitro rooting of alder (Alnus glutinosa (L.) Gaertn) and birch (Betula pendula Roth)

Humic substances (HS) are organic compounds resulting from the physical, chemical and microbiological transformations of organic residues. Present everywhere in the nature; they are taking part in basic functionalities in any ecosystems involving soils, sediments, water and landfills. They are heterogeneous and complex carbon macromolecules. Our study aims to compare the effect of HS from différent sources on in vitro rooting of woody plants.