Pronunciation: [pˈɪnjuːl] (IPA) 
The word "pinnule" is spelled with double "n" and "l" to represent its pronunciation. It is a botanical term that refers to the small leaflet or division of a compound leaf. The IPA phonetic transcription of "pinnule" is /ˈpɪnjuːl/, which shows the stress on the first syllable "pin" and the long "u" sound in the second syllable "u". The final "e" in "pinnule" is silent, as the phonetic transcription suggests.
A pinnule is a term widely used in the field of botany to refer to a small, leaf-like structure or appendage that is characteristic of certain plants and ferns. It is a diminutive form of the word "pinna" which means a primary division of a compound leaf or frond.
Pinnules are typically found on compound leaves, which are leaves that are divided into individual leaflets. These leaflets are attached to the main stem of the leaf or frond by a central axis or rachis. Each pinnule has its own stalk, known as a petiolule, which connects it to the rachis.
Pinnules display a wide range of shapes and sizes depending on the plant species. They may be elongated, oval, lance-shaped, or even finely divided into smaller segments called lobes. Some pinnules possess serrated or toothed edges, while others feature smooth margins. Furthermore, the surface of pinnules can be smooth, glossy, hairy, or even covered in tiny scales, depending on the plant species.
Pinnules play a crucial role in photosynthesis, as they have the ability to capture sunlight and convert it into energy through the process of photosynthesis. Additionally, they aid in the absorption of carbon dioxide and the release of oxygen. Pinnules also assist in reducing water loss through transpiration, as they have a waxy cuticle covering their surface, which helps to prevent excessive evaporation.
Overall, pinnules are essential structures that contribute to the growth, development, and function of plants, particularly those with compound leaves and ferns.
One of the leaflets of a pinnulate leaf.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.
The term pinnule originates from the Latin word pinnula, which is the diminutive form of pinna, meaning feather or fin. In English, pinnule specifically refers to a small, secondary leaflet or a subdivision of a larger leaf in certain plants, such as ferns or palms. The word pinnula itself derives from the Latin word penna, meaning feather.
