Stems are one of the two main structural axes of a vascular plant, the other being the root. They are usually above ground, although some plants have underground stems. Stems may be herbaceous (soft) or woody in nature, and their main function is to provide support to the plant, holding leaves, flowers, and buds/30%3A_Plant_Form_and_Physiology/30.02%3A_Stems_-Functions_of_Stems). They also transport water and dissolved substances between the roots and the shoots in the xylem and phloem, and transport sugars from the leaves to the rest of the plant/30%3A_Plant_Form_and_Physiology/30.02%3A_Stems-Functions_of_Stems). Stems support leaves, flowers, and fruits, and are the main transportation routes of water from the roots to the leaves. They also respond to air movement, to the shortage and surplus of nutrients and water, and they harvest sunlight. Plant stems, whether above or below ground, are characterized by the presence of nodes and internodes. Nodes are points of attachment for leaves, aerial roots, and flowers. The stem region between two nodes is called an internode/30%3A_Plant_Form_and_Physiology/30.02%3A_Stems-_Functions_of_Stems).