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Compound leaves may be pinnate with pinnae (leaflets) on both sides of a rachis (axis), or may be palmate with multiple leaflets arising from a single point. [1] Leaf structure is described by several terms that include: Bipinnate leaf anatomy with labels showing alternative usages A ternate compound leaf with a petiole but no rachis (or rachillae)
paripinnate: pinnately compound leaves in which leaflets are borne in pairs along the rachis without a single terminal leaflet; also called "even-pinnate". imparipinnate: pinnately compound leaves in which there is a lone terminal leaflet rather than a terminal pair of leaflets; also called "odd-pinnate".
The two main classes of compound leaf morphology are palmate and pinnate. For example, a hemp plant has palmate compound leaves, whereas some species of Acacia have pinnate leaves. The ultimate free division (or leaflet) of a compound leaf, or a pinnate subdivision of a multipinnate leaf is called a pinnule or pinnula.
The primary leaf or leaves of a plant embryo which upon germination develops into the seed-leaf or the first set of leaves. craspedodromous Pinnate venation in which the secondary veins terminate at the margin s, often as teeth. crateriform In the shape of a saucer or shallow cup; hemispherical or more shallow. cremnophyte
Petiole – a leaf stalk supporting a blade and attaching to a stem at a node. Petiolule - the leaf stalk of a leaflet. Pulvinus – the swollen base of a petiole or petiolule, usually involved in leaf movements and leaf orientation. Rachilla – a secondary axis of a multiply compound leaf. Rachis – main axis of a pinnately compound leaf.
In a frond which is pinnate (feather-shaped), each leafy segment of the blade is called a pinna (plural pinnae), the stalk bearing the pinna is termed a petiolule, and the main vein or mid-rib of the pinna is referred to as a costa (plural costae). [6] If a frond is divided once into pinnae, the frond is called once pinnate.
Some species have fronds reaching 3–4 m in length, and have a final crown width of some 6 m. The fronds are circinate before unfolding and usually pinnately or bipinnately compound, with deeply pinnately lobed leaflets. The large leaves are covered in scales and hairs, and bear sori (spore clusters) on their undersides. [4]
The leaf base of some palms is also used to extract coir. [citation needed] The oldest leaf forms the outermost layer of the crownshaft. Eventually the lowest palm frond dies back, the outer layer of the crownshaft splits, the leaf unwraps and pulls away from the trunk exposing the new crownshaft surface.