Pinnately compound leaves are a type of compound leaves. Here lamina is divided into multiple leaflets or pinnules. Leaflets are attached to the common axis that is called the rachis. The rachis is the midrib.
Leaves are categorised into simple leaves and compound leaves based on the division in the lamina. Simple leaves are undivided or the incision does not reach the midrib. Compound leaves have their lamina separated into multiple leaflets.
Compound leaves are of two types:
- Pinnately Compound Leaves – Here, leaflets are present on the common axis called the rachis. Leaves are arranged in the opposite manner. Rachis represents the midrib. Leaflets are also called pinnules. E.g. Neem leaf.
- Palmately Compound leaves – Here, leaflets are attached at a single point, that is at the petiole tip. E.g. Silk cotton.
Axillary buds are not present in the axils of leaflets.
Types of Pinnately Compound Leaves
On the basis of the arrangement and number of leaflets, pinnately compound leaves are of the following types:
- Paripinnate – It has an even number of leaflets attached in the opposite manner on the rachis. The rachis ends with the two leaflets. E.g. Tamarind
- Imparipinnate – Odd number of leaflets are present. Leaflets are attached in the opposite manner. A single leaflet is present at the apex of the rachis. E.g. Neem
On the basis of the number of times they are divided, pinnately compound leaves are divided into the following types:
- Unipinnate – These are also called simple pinnate. Here, leaflets are directly attached to the rachis in the opposite manner, e.g. Cassia
- Bipinnate – Here, the primary rachis is branched and leaflets are attached to the secondary rachis, e.g. Acacia
- Tripinnate – Here, the secondary rachis is further divided and leaflets are attached to the tertiary rachis, e.g. Moringa
- Decompound – These leaves are more than thrice pinnate. E.g. coriander
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