HomeenCompound leaves: palmate, pinnate, and bipinnate

Compound leaves: palmate, pinnate, and bipinnate

The leaves are fundamental components of plants: gaseous and water exchange with the atmosphere takes place in them, as well as photosynthesis. They have laminar forms with different arrangements; They are large surfaces exposed to sunlight where the tissues and organs that carry out photosynthesis are displayed along with other vital processes for the plant.

The shapes of the leaves can be very diverse and are usually a characteristic of the species, their classification being dependent on various parameters. In the case of trees, compound leaves are those that have two or more distinct parts attached to the same stem or petiole.

compound leaves compound leaves

A first element to identify a tree species can be to see if it has a simple leaf or a compound leaf, to later move on to other specific aspects such as the shape of the leaves, the bark or its flowers and seeds. Once you have identified that it is a tree with compound leaves, you can try to see which of the three generic types of compound leaves it can be associated with. These three classes of compound leaves are palmate, pinnate, and bipinnate leaves. These three classes are part of a form of classification based on the morphology of the leaves, which is used to study plants and define their genus and species. The morphological classification includes the description of the venation of the leaf, its general shape and that of its edges, as well as the arrangement of the stem.

The subcomponents of the palmate leaves radiate from a point of attachment to the branch called the distal end of the petiole or rachis. They get their name from the resemblance of this leaf format to the palm and fingers of a hand.

The pinnately compound leaves are structured with small twigs of different lengths radiating along the petiole, from which leaves of different shapes and sizes grow. This leaf shape resembles in some cases the distribution of a feather. When the small twigs that are distributed along the petiole of a leaf are, in turn, pinnate, they are called bipinnate compound leaves.

palmate compound leaves

palmate compound leaf palmate compound leaf

The palmately compound leaves are distributed from a point at the end of the petiole and may be composed of three or more parts, depending on the genus of tree. In this type of leaf, each section that radiates from the point of union, the axil, is part of the leaf, so it can be confused with the simple leaves formed in branches with a cluster distribution. The palmate leaves do not have a rachis, an axis of structuring or irradiation, but their parts are united in the petiole. The chestnut leaves shown in the figure above are an example of palmate leaves.

Pinnately compound leaves

pinnate compound leaf pinnate compound leaf

The pinnately compound leaves display small leaves from a vein, a rachis, and the whole forms the leaf that is attached to the petiole or stem. Ash leaves are an example of a pinnate compound leaf.

bipinnate compound leaves

bipinnate compound leaf bipinnate compound leaf

The bipinnate compound leaves are often confused with similar leaves such as those of ferns; however, these are different plants, they are not trees. The bipinnate compound leaves are like the pinnate ones but instead of leaves distributed along the rachis, they display secondary rachis along the primary one, and from these secondary rachis the leaves emerge. The acacia leaves in the figure above are an example of a bipinnate compound leaf.

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González, AM, Arbo, MM Organization of the body of the plant; the sheet . Morphology of vascular plants. National University of the Northeast, Argentina, 2009.

Compound leaf forms . Botanipedia.