What is the thickened part of the stem?

The thickened part of a stem is typically referred to as a "node." Nodes are the points on the stem where leaves, branches, or flowers can grow. They play a crucial role in the plant's structure and development, as they support the attachment of these components and can also be involved in the storage of nutrients. In some plants, thickened stems can serve as storage organs, like tubers or rhizomes.