Q:

What is the purpose of the cotyledon in a seed?

A:

Quick Answer

The cotyledon, which forms in the embryo of a seed before germination, stores food for the embryo. Along with the endosperm, the cotyledon nourishes the new growth of the plant. It is the part of the seed that emerges from the testa, or hard covering, during germination. It sometimes grows upward, turning into a set of leaves as the seed germinates, using photosynthesis to nourish the newly forming plant further.

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Full Answer

The leaves formed by the cotyledon sometimes drop off as the plant's first real leaves, which look different from the leaves formed by the cotyledon, emerge. Other times, they remain a part of the plant for years. A cotyledon may also remain underground rather than shooting up as a set of leaves, where it functions as a storage area for food for the plant.

Seeds can have one cotyledon or a pair of cotyledons. Those with one are called monocots, while those with two are classified as dicots. Seeds that are dicots have cotyledons that function as leaves, while monocots have cotyledons that are appendages for food storage. Seeds that store their food in cotyledons inside the embryo are called exalbuminous. Seeds can remain in a dormant state for years, only germinating when conditions are right.

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Related Questions

  • Q:

    What is epigeal and hypogeal germination?

    A:

    In hypogeal germination, cotyledons remain inside the seed shell, beneath the ground and non-photosynthetic, while in epigeal germination, the cotyledons expand to split the seed coat, allowing the sprout to push them above the ground where they become photosynthetic, according to Reference.com. Epigeal germination allows the young plants to begin providing food quickly as the cotyledons have little food stored to provide for their needs.

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  • Q:

    How does salt affect seed germination?

    A:

    High concentrations of salt in soil generally reduce the rate of seed germination. Increased salt levels prevent essential water from seeping into the seed. The lack of moisture retards its growth and development, which may cause the seed to wilt and eventually die.

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  • Q:

    Why don't seeds need sunlight to germinate?

    A:

    Seeds typically do not require sunlight for germination because most of their nutritional needs for the germination phase of a plant's life are contained within the seed itself. Conversely, some seeds do require light to germinate. Although this is atypical, such seeds mustn't be buried in soil.

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  • Q:

    What are the five stages of seed germination?

    A:

    Seed germination begins when the first root breaks through the seed wall and ends when the first pair of true leaves begin the process of photosynthesis. The three stages in-between are when the primary root, which is called the radicle, develops root hairs, the first young shoot rises emerges from the soil and the first pair of true leaves form to begin to manufacture food for the plant.

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