leafsheath

Leaf sheath is the basal portion of a monocot leaf that wraps around the stem, enclosing the culm for part of its length. It is a primary component of many grasses, sedges, and bamboos, with the leaf blade (lamina) emerging from its upper margin at the leaf collar. The sheath commonly extends from the leaf base to the point where the blade begins, and its margins may be fused or only loosely enclosing the stem, depending on species. At the junction with the blade, a collar is often present, sometimes accompanied by a ligule— a small membranous or hairy structure— and in some species by auricles.

Anatomical variation is common among taxa. Leaf sheaths vary in length and thickness and may be closed along their length or show a seam or opening. In grasses, the sheath can remain around the stem for much of the leaf’s life, or shed with leaf turnover in some cases. The presence and form of ligules and auricles are frequently used in identifying and distinguishing species within Poaceae and related groups.

Functions of the leaf sheath include providing mechanical support to the leaf and stem, protecting the growing meristem at the leaf base, and aiding in moisture management and leaf positioning for photosynthesis. The architecture of the sheath contributes to the overall plant form, especially in grasses and bamboos, where it can be a prominent feature of leaf anatomy and plant habit.