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How do cotyledons help a young tree seedling grow?

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Tall giant sequoia trees with reddish bark and thick trunks rise closely together in a dense forest at Sequoia National Park, California. — tree A stand of giant sequoia trees (*Sequoiadendron giganteum*) in Sequoia National Park, California.

Cotyledons, or seed leaves, are essential for the early development of a young tree seedling before it becomes nutritionally self-supporting. Their primary role is to supply the nutrition necessary for the embryo to germinate and establish itself as a photosynthetic organism.1

Depending on the species, cotyledons assist growth in the following ways:

Nutrient Storage and Mobilization: In many seeds, cotyledons act as a storage site for nutritional reserves, such as starch, proteins, and lipids. They mobilize these materials and deliver them to the developing radicle and epicotyl.1
Nutrient Absorption: In some cases, cotyledons function as specialized organs that absorb nutrients from the endosperm or the female gametophyte, digesting and translocating these reserves to the growing embryo.12
Photosynthesis: Once the seedling emerges, cotyledons may expand in the light to develop chlorophyll and perform photosynthesis, providing the energy required for the seedling to grow until it develops its first true leaves.12

Whether they remain underground or emerge above the soil, these embryonic leaves are vital for sustaining the seedling until it can independently produce its own food.1