Explain hypogeal germination in details
Hypogeal germination is a type of seed germination in which the cotyledons (embryonic leaves) remain below the ground after germination. This is in contrast to epigeal germination, where the cotyledons emerge above the ground.
During hypogeal germination, the first visible sign of germination is the emergence of the radicle (embryonic root) from the seed coat. The radicle grows downwards into the soil, anchoring the seedling and absorbing water and nutrients from the soil. As the radicle elongates, the embryo and cotyledons begin to also grow.
In hypogeal germination, the cotyledons do not come out of the soil, instead, they remain in the seed or push through the soil up to a certain extent. The stem and epicotyl (part of the embryo above the cotyledons) grow upward, pulling the cotyledons back down into the soil. The cotyledons then stay within the soil, serving as a source of stored energy for the developing seedling.
The stem and epicotyl continue to elongate, pushing the first true leaves above the ground. These are the leaves that are photosynthetic and responsible for the production of food for the plant. The cotyledons, although remaining underground, may continue to function in providing nutrients to the developing seedling until they wither away.
Hypogeal germination is commonly seen in plants such as beans, peanuts, and peas. These plants have relatively large cotyledons that are packed with nutrients, making them suitable for storage until the seedling is established and able to photosynthesize on its own.
Overall, hypogeal germination allows for the efficient and protected development of the seedling, as the cotyledons serve as a source of nutrients while remaining below the surface. This strategy ensures that the seedling has access to sufficient energy to survive and grow until it can produce its own food through photosynthesis.