Effect of Phosphate Deficit on Root Growth, Production of Reactive Oxygen Species and Hormone Content in Barley Plants

Abstract

The article presents the results of research into the effect of removing phosphate from a nutrient medium on the content of auxins and cytokinins in roots, root elongation and content of reactive oxygen species in root tips of the barley ‘Steptoe’. In our experiments, the growth response was detected as root elongation after a 4-day exposure to a phosphate-free medium. Activation of linear root growth was preceded by changes in hormonal balance and in the level of reactive oxygen species. Auxin content in the roots increased after 6 h of phosphate starvation and a two-fold increase in the concentration of auxins in roots was detected by the end of the first day of the exposure to the phosphate deficit conditions. Staining with diaminobenzidine revealed an increased level of reactive oxygen species in the root tips of phosphate-starved plants after 6 h of exposure. However, after one day (24 h), a reverse pattern was observed: the level of staining was higher in the plants supplied with phosphates. Immunolocalisation of cytokinins in the root tips, where the zones of cell division and extension determining root elongation are located, showed a decreased content of zeatin in the cells under the effect of phosphorus deficit. The obtained data suggest that the detected rise in the amount of reactive oxygen species was due to the increased concentration of auxins accumulated as a result of the phosphate deficit effect on the barley plants. The increase in ROS and auxins contents could in turn influence the level of cytokinins and, in the end, affect root elongation. Further experiments are needed to test this hypothesis

Keywords

• hordeum vulgare
• phosphate deficit
• root growth
• auxins
• cytokinins
• reactive oxygen species
• hordeum vulgare