3.3.1: Stem Morphology (External Structure)

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Page ID: 37047

Melissa Ha, Maria Morrow, & Kammy Algiers
Yuba College, College of the Redwoods, & Ventura College via ASCCC Open Educational Resources Initiative

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Learning Objective

Identify the main external structures of the shoot system, including the nodes, internodes, leaves, axillary buds, and axillary shoots.

Plant stems, whether above or below ground, are characterized by the presence of nodes and internodes (Figure \(\PageIndex{1}\)). Nodes are points of attachment for leaves. Leaves often consist of a thin region that attaches to the stem (the petiole) and a broader blade (see Leaves). The stem region between two nodes is called an internode. 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 called an axillary shoot (Figure \(\PageIndex{2}\)). The shoot apex at the tip shoot contains the shoot apical meristem surrounded by developing leaves called leaf primordia (see Meristems).

Close-up view of a shoot with nodes, internodes, and leaves labeled — Figure \(\PageIndex{1}\): Leaves are attached to the plant stem at areas called nodes. An internode is the stem region between two nodes. The smaller leaves just above the nodes are the beginning of axillary shoots, which arose from axillary buds. Image modified from OpenStax (CC-BY)

An arrow marks a rounded point emerging where a leaf petiole attaches to the stem — Figure \(\PageIndex{2}\): Axillary buds of sweet granadilla (*Passiflora ligularis*). One of the axillary buds is labeled with an arrow. Image modified from Eiku (CC-BY-SA).

Attributions

Curated and authored by Melissa Ha from 30.2 Stems from Biology 2e by OpenStax (licensed CC-BY)