Hypocotyl
/ˌhaɪpəˈkɑtəl/
Definition
Hypocotyl refers to the part of a seedling stem located below the cotyledons, or seed leaves, and above the root. It is a plant structure present during early development. In many seedlings, the hypocotyl elongates as the seed germinates, helping lift the cotyledons above the soil. It differs from the epicotyl, which is the stem section above the cotyledons and bears the first true leaves.
Function in Plants
- Seedling emergence: In many seedlings, the hypocotyl elongates and lifts the cotyledons above the soil surface, helping the young plant reach light soon after germination.
- Link between root and shoot: The hypocotyl connects the developing root system below with the cotyledons and first shoot structures above, making it an important transition zone in early growth.
- Variation among germination types: Its growth pattern differs between epigeal and hypogeal germination. That difference helps botanists describe how species establish after sprouting.
- Practical nursery relevance: Growers often watch the hypocotyl in seedlings because abnormal stretching can indicate low light, while stem collapse near this region may signal damping-off, a disease that kills young seedlings.
Related Terms
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