The present invention relates to methods for stimulating root growth and/orenhancing the formation of lateral or adventitious roots and/or altering rootgeotropism comprising expression of a plant cytokinin oxidase or comprisingexpression of another protein that reduces the level of active cytokinins inplants or plant parts. The invention also relates to novel plant cytokininoxidase proteins, nucleic acid sequences encoding cytokinin oxidase proteinsas well as to vectors, host cells, transgenic cells and plants comprising saidsequences. The invention also relates to the use of said sequences forimproving root-related characteristics including increasing yield and/orenhancing early vigor and/or modifying root/shoot ratio and/or improvingresistance to lodging and/or increasing drought tolerance and/or promoting invitro propagation of explants and/or modifying cell fate and/or plantdevelopment and/or plant morphology and/or plant biochemistry and/or plantphysiology. The invention also relates to the use of said sequences in theabove-mentioned methods.The invention also relates to methods for identifyingand obtaining proteins and compounds interacting with cytokinin oxidaseproteins. The invention also relates to the use of said compounds as a plantgrowth regulator or herbicide.
