The present invention relates to methods for stimulating root growth
and/or enhancing the formation of lateral or adventitious roots and/or
altering root geotropism comprising expression of a cytokinin oxidase or
comprising expression of another protein that reduces the level of active
cytokinins in plants or plant parts. Also provided by the present
invention are methods for increasing seed size and/or weight, embryo size
and/or weight, and cotyledon size and/or weight. The methods comprise
expression of a cytokinin oxidase or expression of another protein that
reduces the level of active cytokinins in plants or plant parts. Methods
and compositions for increasing seed yield are also provided. The
invention also relates to isolated plant cytokinin oxidase proteins,
nucleic acid sequences encoding cytokinin oxidase proteins as well as to
vectors, host cells, transgenic cells and plants comprising such
sequences. The use of these sequences for improving root-related
characteristics including increasing yield and/or enhancing early vigor
and/or modifying root/shoot ratio and/or improving resistance to lodging
and/or increasing drought tolerance and/or promoting in vitro propagation
of explants and/or modifying cell fate and/or plant development and/or
plant morphology and/or plant biochemistry and/or plant physiology, is
also provided. The invention also relates to methods for identifying and
obtaining proteins and compounds interacting with cytokinin oxidase
proteins as well as the use of such proteins and/or compounds as plant
growth regulators or herbicides.
