In the diagram, the part marked I will contain a high concentration of

In the diagram, the part marked I will contain a high concentration of auxin. Auxin is a plant hormone that plays a variety of roles in plant growth and development, including promoting cell elongation, regulating apical dominance, and initiating the formation of roots. The part marked I in the diagram is the tip of a plant shoot, which is the site of active cell division and growth. Auxin is produced in the tip of the shoot, and then transported downward through the plant to the roots. This means that the concentration of auxin is highest in the tip of the shoot, which is where the hormone is synthesized. Ascorbic acid, abscisic acid, and ethylene are also plant hormones, but they are not primarily associated with the tip of the shoot or with promoting cell elongation.