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How do cotyledons support a young plant after germination?
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seed
Fruit and seeds of the southern magnolia (Magnolia grandiflora). The fruit is an aggregate of follicles, and each follicle bears a single red seed.
Cotyledons, or seed leaves, are essential for supporting a young plant during the critical period after germination before it becomes nutritionally self-supporting. Their primary roles include:
- Nutrient Storage and Mobilization: In many species, cotyledons store the nutritional reserves (such as starch, proteins, and lipids) required for early growth. They mobilize these materials and deliver them to the developing radicle and epicotyl. In other cases, they act as specialized absorbing organs that extract nutrients from the endosperm and transfer them to the seedling.12
- Photosynthesis: In some plants, such as the castor bean, the cotyledons emerge aboveground, expand, and develop chlorophyll to function as the plant's first photosynthetic organs.12
- Structural Support: Depending on the germination pattern, cotyledons may remain underground (hypogeal) or be raised aboveground (epigeal) by the elongating hypocotyl. Once their stored reserves are exhausted or the plant establishes itself, these embryonic leaves typically degenerate.12
By providing these vital resources, cotyledons ensure the seedling can survive until it is capable of independent growth and reproduction.12