Effect of phosphorus starvation on hormone content and growth of barley plants

To address the question of the role of phytohormones in the growth responses induced by P availability, we compared the effects of low P on the growth of barley plants, and the contents of auxin, cytokinins and abscisic acid (ABA). Comparative study of the changes in growth and hormones' levels in response to P-starvation showed that relative activation of root growth may be related to the decline in shoot cytokinin content and ABA accumulation in the roots of P-starved (P-) barley plants. The decline in shoot cytokinins is likely to result from the inhibition of the transport of these hormones from roots, and in turn, may contribute to increased distribution of auxins in favor of roots. Reduced root branching detected in our experiments, despite maintenance of root auxins, may be related to an elevated level of either cytokinins or ABA in roots of P- barley plants. Thus, interactions between auxins, cytokinins and ABA are likely to be responsible for the changes in root architecture in P- plants.