Oxidative Stress and Formation and Maintenance of Stem Root Cells
In the root tip, there is a small group of cells that, in contrast to surrounding cells, divide very seldom. This group of cells was named "quiescent center". There is ample evidence that cells of the plant quiescent center are very similar to mammalian stem cells. The redox status of quiescent center cells differs from that of adjacent rapidly dividing cells. The hypothesis of L. Feldman and his coworkers, according to which a more oxidizing environment in the quiescent center cells results from the high activity of ascorbate oxidase activated by indolyl acetic acid accumulating in these cells, is discussed. The high activity of ascorbate oxidase is responsible for lowered concentrations of reduced form of ascorbic acid and glutathione and high content of ROS in quiescent center cells. The oxidative stress represses the cell proliferation. Inhibitors of IAA transport attenuate the oxidative stress, thus suggesting a role of IAA as an activator of ascorbate oxidase. Interestingly, the high concentration of IAA in dividing cap cells adjacent to quiescent center cells did not cause the retardation of cell proliferation and oxidative condition in these cells.