30.2: Stems - Functions of Stems
- Summarize the main function and basic structure of stems
Stems
Stems are a part of the shoot system of a plant. They may range in length from a few millimeters to hundreds of meters. They also vary in diameter, depending on the plant type. Stems are usually above ground, although the stems of some plants, such as the potato, also grow underground. Stems may be herbaceous (soft) or woody in nature. Their main function is to provide support to the plant, holding leaves, flowers, and buds; in some cases, stems also store food for the plant. A stem may be unbranched, like that of a palm tree, or it may be highly branched, like that of a magnolia tree. The stem of the plant connects the roots to the leaves, helping to transport absorbed water and minerals to different parts of the plant. The stem also helps to transport the products of photosynthesis (i.e., sugars) from the leaves to the rest of the plant.
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. The stalk that extends from the stem to the base of the leaf is the petiole. An axillary bud is usually found in the axil (the area between the base of a leaf and the stem) where it can give rise to a branch or a flower. The apex (tip) of the shoot contains the apical meristem within the apical bud.
Key Points
- Most stems are found above ground, but some of them grow underground.
- Stems can be either unbranched or highly branched; they may be herbaceous or woody.
- Stems connect the roots to the leaves, helping to transport water, minerals, and sugars to different parts of the plant.
- Plant stems always have nodes (points of attachments for leaves, roots, and flowers) and internodes (regions between nodes).
- The petiole is the stalk that extends from the stem to the base of the leaf.
- An axillary bud gives rise to a branch or a flower; it is usually found in the axil: the junction of the stem and petiole.
Key Terms
- node : points of attachment for leaves, aerial roots, and flowers
- internode : a section of stem between two stem nodes
- petiole : stalk that extends from the stem to the base of the leaf
- axillary bud : embryonic shoot that lies at the junction of the stem and petiole that gives rise to a branch or flower