I'm not sure it's possible to give a reason, it's just evolution providing a slightly different solution to propogate the species, here's some reference material that might help:
epigeal
In botany, a seed is described as epigeal when the cotyledons of the germinating seed expand, throw off the seed shell and become photosynthetic above the ground.
The converse, where the cotyledons remain non-photosynthetic, inside the seed shell, and below ground, is hypogeal.
cotyledon
Cotyledons may be either epigeal, expanding on the germination of the seed, throwing off the seed shell and become photosynthetic above the ground; or hypogeal, not expanding, remaining below ground and not becoming photosynthetic. The latter is typically the case where the cotyledons act as a storage organ, as in many nuts and acorns.
There maybe some slightly different environmental factors that favor one approach over the other, but that's just a guess.
Here's some more: http://www.answers.com/topic/germination
I'm no expert but I think this might help:
From: http://www.answers.com/topic/epigeal In botany, a seed is described as epigeal when the cotyledons of the germinating seed expand, throw off the seed shell and become photosynthetic above the ground. The converse, where the cotyledons remain non-photosynthetic, inside the seed shell, and below ground, is hypogeal. And http://www.answers.com/topic/cotyledon Cotyledons may be either epigeal, expanding on the germination of the seed, throwing off the seed shell and become photosynthetic above the ground; or hypogeal, not expanding, remaining below ground and not becoming photosynthetic. The latter is typically the case where the cotyledons act as a storage organ, as in many nuts and acorns.
So as the seed of oil seed crops does not act as a storage organ, they are typically epigeal in nature.
Here's some more: http://www.answers.com/topic/germination
Germination is the process where a seed sprouts and begins to grow into a new plant. There are two main types of germination: epigeal germination, where the cotyledons emerge above the soil surface, and hypogeal germination, where the cotyledons remain below the soil surface. Epigeal germination is commonly seen in beans and peas, while hypogeal germination is typical in plants like sunflowers and corn.
Epigeal germination is when the seedling emerges above the soil surface, while apogeal germination is when the seedling remains below the soil surface. In epigeal germination, the cotyledons become photosynthetic and green, while in apogeal germination, the cotyledons remain underground and non-photosynthetic.
Seed germination helps plants survive by allowing them to grow and develop into mature plants that can reproduce. It also helps plants establish themselves in new environments and compete for resources. Additionally, germination can help plants adapt to changing environmental conditions and ensure genetic diversity within populations.
Epigeal germination is a type of seed germination where the cotyledons emerge above the soil surface after germination. In this process, the stem grows upward sharply, carrying the cotyledons above the ground, while the roots grow downward. It is commonly seen in dicot plants.
Methi seeds exhibit epigeal germination, where the cotyledons emerge above the ground during germination. This type of germination allows for the efficient exposure of the cotyledons to sunlight for photosynthesis.
in epigeal germination cotyledons and plumule comes out from soil in hypogeal germinatin only plumule comes out from soil
Epigeal germination occurs when the cotyledons emerge above the ground during germination, such as in beans and sunflowers. Hypogeal germination is when the cotyledons remain below the ground, like in peas and peanuts.
Epigeal germination is when the cotyledons emerge above the soil surface during seed germination. Hypogeal germination is when the cotyledons remain below the soil surface during seed germination.
no it is epigeal type of germination because the cotyledons are under the soil
Well, hello there! Cowpeas, like many legumes, undergo hypogeal germination, where the cotyledons stay below the ground. This process helps protect the delicate cotyledons as the seedling emerges, allowing it to grow strong and healthy. Just like a happy little seedling reaching for the sun, cowpeas follow their own beautiful path of growth.
hypogeal
The two main types of germination are epigeal germination, where the cotyledons emerge above the soil surface, and hypogeal germination, where the cotyledons remain below the soil surface. Epigeal germination is common in dicot plants, while hypogeal germination is common in monocot plants.
Germination is the process where a seed sprouts and begins to grow into a new plant. There are two main types of germination: epigeal germination, where the cotyledons emerge above the soil surface, and hypogeal germination, where the cotyledons remain below the soil surface. Epigeal germination is commonly seen in beans and peas, while hypogeal germination is typical in plants like sunflowers and corn.
Epigeal germination is the process in which the seed leaves or the cotyledons are brought on to the surface along with the shoot during germination. Hypogeal germination is the process in which the seed leaves or the cotyledons remain below the soil surface during germination.
I'm no expert, but I believe yes: From: http://www.answers.com/topic/epigeal In botany, a seed is described as epigeal when the cotyledons of the germinating seed expand, throw off the seed shell and become photosynthetic above the ground. The converse, where the cotyledons remain non-photosynthetic, inside the seed shell, and below ground, is hypogeal. And http://www.answers.com/topic/cotyledon Cotyledons may be either epigeal, expanding on the germination of the seed, throwing off the seed shell and become photosynthetic above the ground; or hypogeal, not expanding, remaining below ground and not becoming photosynthetic. The latter is typically the case where the cotyledons act as a storage organ, as in many nuts and acorns. And http://www.answers.com/topic/germination
Some seeds that undergo epigeal germination include beans, peas, peanuts, sunflower seeds, and most types of dicot plants. In epigeal germination, the cotyledons are pushed above the soil surface as the seedling emerges.
Epigeal germination is when the seedling emerges above the soil surface, while apogeal germination is when the seedling remains below the soil surface. In epigeal germination, the cotyledons become photosynthetic and green, while in apogeal germination, the cotyledons remain underground and non-photosynthetic.