In the present work we have studied the effect of phosphate withdrawal from the nutrient medium on the content of auxins and cytokinins in the roots, their elongation and ROS content in the root tips of barley parts. The obtained results suggest possible succession of events, when phosphate deficit results in the changes in the ROS level brought about by accumulation of auxins resulting in turn in the changes in cytokinins level and elongation of roots. Further experiments are needed to test this hypothesis.