pinnataan

Pinnataan, in botanical usage, describes a leaf arrangement in which a leaf is compound and its leaflets are borne along a central axis called the rachis, on both sides in a featherlike pattern. The whole leaf is typically attached to the stem by a petiole, while each leaflet is usually connected to the rachis by a small stalk called a petiolule. Pinnate leaves can be further classified as odd-pinnate, with a terminal leaflet, or even-pinnate, lacking a terminal leaflet. In some species the leaf may be bipinnate, meaning that the leaflets are themselves divided into secondary leaflets on shorter axes.

Pinnation is contrasted with other compound-leaf patterns, such as palmate leaves, where leaflets radiate from a single point at the tip of the petiole rather than along a central rachis. The degree of division and the arrangement of leaflets are important for plant identification and taxonomy and can vary between species and environments. The term reflects a general asymmetry along the longitudinal axis rather than a radial arrangement.

Examples of plants with pinnate leaves include many species in the Fabaceae, Oleaceae, and Anacardiaceae families, among others. Azadirachta indica (neem) typically shows imparipinnate leaves with multiple leaflets; Fraxinus (ash) species also exhibit pinnate leaves with several leaflets per leaf. Understanding pinnation helps in recognizing plant groups and interpreting how leaf morphology relates to function such as light capture and wind resistance.

Etymology traces pinnation to Latin pinnatus, meaning feathered, from pinna, feather. In Indonesian and Malay, the term pinnataan is used to describe this leaf arrangement in dicotyledonous plants.