The present invention relates to a genetic construct comprising a nucleic acid sequence encoding cytokinin biosynthetic isopentenyl-transferase enzyme (IPT) operable linked to a promoter allowing expression of said nucleic acid sequence in cambial cells. The invention relates also a method for producing a transgenic plant capable of increased biomass production and/or increased stem volume growth compared to wild type plant and a method for improving the production of biomass and/or increased stem volume growth in trees, as well as to a tree that over expresses an endogenous or exogenous nucleic acid sequence encoding IPT in cambial cells and a wood product obtainable from the transgenic tree.
