Cotyledons

Cotyledons are a significant part of the embryo within the seed of a plant. They serve as the initial leaves that emerge during germination and play a crucial role in the plant's early development. Depending on the species, a seed can have one (monocotyledons) or two (dicotyledons) cotyledons. This classification forms the basis for one of the major divisions within the angiosperms (flowering plants), which are the largest group of plants on Earth.

Function

Cotyledons serve several essential functions in a plant's life cycle. They act as food storage organs, containing nutrients that support the early growth of the plant after germination. In some species, cotyledons are photosynthetic and emerge above the soil surface, functioning as the seedling's first leaves. In others, they remain underground, absorbing nutrients from the endosperm and transferring them to the developing plant.

Classification

The presence of one or two cotyledons is a key feature used to classify flowering plants into two major groups:

• Monocotyledons (monocots) have a single cotyledon. This group includes plants such as grasses, lilies, and orchids.
• Dicotyledons (dicots) have two cotyledons. This group encompasses a wide variety of plants, including roses, peas, and oak trees.

This distinction is not only important for botanical classification but also influences the plant's overall growth pattern, leaf shape, and flower structure.

Development

Cotyledon development is a critical phase of the plant life cycle. During seed germination, the cotyledons may either become the embryonic first leaves of a seedling or act as a source of nutrients for the developing seedling. The process is regulated by various environmental factors, including temperature, light, and water availability, as well as by internal hormonal signals within the plant.

Evolutionary Significance

Cotyledons are considered an evolutionary adaptation that has allowed flowering plants to become the most diverse and widespread group of plants on Earth. They enable efficient nutrient storage and use during the early stages of germination and seedling establishment, which can be crucial for survival in competitive natural environments.

See Also

• Seed germination
• Angiosperms
• Plant morphology