siemenilehden

Siemenilehden, or cotyledon in Finnish botany, refers to the embryonic leaf within a seed-bearing plant. The term combines siemen (seed) and lehti (leaf) and is used to describe the first leaves that develop from the embryo during seed germination. In plant development, cotyledons serve as the primary source of nutrients for the growing seedling.

Function and development: Cotyledons store and transfer nutrients such as starches, oils, and proteins to the developing embryo until the seedling can perform photosynthesis. In many dicotyledonous plants, the two cotyledons unfold to form the first pair of leaves, often called seed leaves. In monocotyledons, there is typically a single cotyledon that frequently functions to absorb the endosperm and may be less involved in photosynthesis at early stages. Depending on the species, cotyledons may persist underground or emerge above ground and contribute to photosynthesis for a period after germination.

Variation and significance: The number of cotyledons is a key difference between major plant groups—one cotyledon in monocots and two in many dicots. Some seeds retain or rely on endosperm for nourishment rather than on cotyledons themselves. Cotyledons are important in botany and agriculture as indicators of seedling type and early development, and they play a central role in studies of germination and seed evolution.

See also: cotyledon, germination, embryo, endosperm.