What is the Difference Between Epigeal and Hypogeal Germination?

Epigeal and hypogeal germination are two types of seed germination processes that differ in the position of the cotyledons relative to the soil surface during and after germination. The main differences between epigeal and hypogeal germination are:

1. Position of Cotyledons: In hypogeal germination, the cotyledons remain below the soil surface, while in epigeal germination, the cotyledons are pushed above the ground.
2. Epicotyl and Hypocotyl Elongation: In hypogeal germination, the epicotyl elongates, and the cotyledons stay in the ground, whereas in epigeal germination, the hypocotyl elongates, and the cotyledons come out of the ground.
3. Cotyledon Function: In hypogeal germination, the cotyledons do not perform photosynthesis and serve as a food source for the growing seedling. In epigeal germination, the cotyledons perform photosynthesis because the cotyledonary leaves are present.
4. Examples: Examples of plants with hypogeal germination include coconut and gram, while examples of plants with epigeal germination include onion and bean.

In both types of germination, the cotyledons and endosperm contain reserved food materials that are hydrolyzed by enzymes when the seed imbibes water, making the nutrients available for the germinating seed.

Comparative Table: Epigeal vs Hypogeal Germination

Here is a table comparing the differences between epigeal and hypogeal germination:

Epigeal germination occurs when the cotyledons emerge above the soil surface, and the hypocotyl elongates, allowing the plumule to come out of the seed coat. In contrast, hypogeal germination takes place when the cotyledons remain below the soil surface, and the epicotyl elongates, enabling the plumule to emerge from the seed coat.