Cotyledons are essentially the seed leaves of a plant embryo. They are the first leaves to emerge from a germinating seed.
Function and Importance
- Initial Nourishment: Cotyledons often contain stored food reserves (endosperm) that nourish the seedling during its early growth stages until it can perform photosynthesis efficiently. This acts as an energy source for the developing plant.
- First Photosynthetic Structures: In some plants, the cotyledons become photosynthetic, producing food for the seedling until the true leaves develop.
- Taxonomic Significance: The number of cotyledons present in a seed is a key characteristic used to classify flowering plants (angiosperms).
Types of Plants Based on Cotyledon Number
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Monocotyledons (Monocots): These plants have one cotyledon. Examples include grasses, lilies, and corn.
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Dicotyledons (Dicots): These plants have two cotyledons. Examples include beans, roses, and sunflowers.
Cotyledon Behavior After Germination
After germination, cotyledons may:
- Expand and Become Photosynthetic: In some dicots, cotyledons function as the first leaves and carry out photosynthesis until true leaves develop.
- Wither and Fall Off: In other plants, cotyledons provide initial nourishment but then shrivel and drop off as the plant establishes itself.
- Remain Underground: Some plants have cotyledons that stay within the seed coat and underground, providing nourishment to the developing seedling without emerging.
