ETYM Old Eng. leef, lef, leaf, as. leáf; akin to s. lôf, OFries. laf, Dutch loof foliage, German laub, Old High Germ. loub leaf, foliage, Icel. lauf, Swed. löf, Dan. löv, Goth. laufs; cf. Lith. lapas. Related to Lodge.
Lateral outgrowth on the stem of a plant, and in most species the primary organ of photosynthesis. The chief leaf types are cotyledons (seed leaves), scale leaves (on underground stems), foliage leaves, and bracts (in the axil of which a flower is produced).
Typically leaves are composed of three parts: the sheath or leaf base, the petiole or stalk, and the lamina or blade. The lamina has a network of veins through which water and nutrients are conducted. Structurally the leaf is made up of mesophyll cells surrounded by the epidermis and usually, in addition, a waxy layer, termed the cuticle, which prevents excessive evaporation of water from the leaf tissues by transpiration. The epidermis is interrupted by small pores, or stomata, through which gas exchange between the plant and the atmosphere occurs.
A simple leaf is undivided, as in the maple or oak. A compound leaf is composed of several leaflets, as in the blackberry, horse chestnut, or ash (the latter being a pinnate leaf). Leaves that fall in the autumn are termed deciduous, while evergreen leaves are persistent.
(Irregular plural: leaves).
1. A sheet of any written or printed material; SYN. folio.
2. Hinged or detachable flat section (as of a table or door).
3. The main organ of photosynthesis and transpiration in higher plants; SYN. leafage, foliage.
Any node (location) in a tree structure that is at the farthest distance from the root (primary node), no matter which path is followed. Thus, in any tree, a leaf is a node at the end of a branch—one that has no descendants. See also root, subtree, tree.
1. To produce leaves, of plants.
2. To turn over pages
3. To turn over the pages of