Blattscheide

Blattscheide (leaf sheath) is the basal portion of a monocot leaf that surrounds and clasps the stem, particularly in grasses. The leaf blade typically emerges from the upper part of the sheath, which forms a tubular envelope around the culm (stem). In many species the sheath is created by two leaf bases that come together along a seam; it can be closed, fully enclosing the stem, or open along a longitudinal slit that leaves part of the stem exposed.

Key structural features include the ligule, a small membranous appendage at the blade–sheath junction, and in some species auricles, which are lobes at the sides of the sheath that may grip the stem. The exact form of the sheath, whether tight or more lax, varies among species and contributes to grass identification and taxonomy.

Functionally, the Blattscheide protects the growing shoot and provides mechanical support to the leaf and, indirectly, to the stem. It helps shield the young meristem from damage and desiccation as the plant develops. While the blade is the primary organ for photosynthesis, the sheath can contribute to photosynthesis to a limited extent in some grasses. The sheath may persist as the plant grows, or parts of it may wither or split, depending on the species.

Occurrence is widespread among monocots, especially in the grass family (Poaceae). It is common in crops such as rice, wheat, and maize, as well as many wild grasses. The structure and properties of the Blattscheide are important for plant anatomy, ecology, and systematic classification.

See also: Leaf anatomy; ligule; auricle; grass.