Radiography of the 46 tooth in a 7-year-old child revealed parallel root walls with a gradual decrease of their thickness resulting in pointed ends. There is a root canal narrowing in the region that is adjacent to the tooth cavity, and a widening at the nascent apical aperture. Periodontal ligament space has a uniform width over the entire root length. In the periapical region it merges with the growth zone. Specify the stage of the root development: