Definition and Process of Hypogeal Germination with Examples
Germination refers to a fundamental process in which we grow the sown plant seeds into younger plants or seedlings. Based on the growing conditions and the cotyledons' fate, there are two types of germination processes, as follows:
Epigeal germination
Hypogeal germination
This article is essential for the Biology students to get a brief idea about germination, its types, and hypogeal germination. It covers all the fundamentals of the concepts and includes some FAQs related to the examinations to assure the students' best practice and understanding.
Define Hypogeal Germination
A hypogeal germination is a form of seed germination that occurs mainly for both monocot and dicot seeds. The cotyledons stay inside the soil due to quicker growth and development in the epicotyl's length. Hypogeal germination is derived from an ancient Greek word, referring to the meaning 'below ground'. Here is a description of the hypogeal germination process:
Cotyledons :
A significant part of the embryo of the seed stays under the soil.
Plumule:
The rudimentary shoot tip that rises from the seed embryo grows above the ground.
Plumule rises and pushes itself upwards.
This process continues with epicotyl – the seed system that stays above the cotyledon and rapidly elongates its structure and shape.
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What is the Hypogeal Germination Process?
After the epicotyl's length grows and develops ultimately, it assumes a curved curvature, causing the plumule to rise above the soil surface and pushing the cotyledons to stay below the surface. In these types of germination, the plumule rapidly grows in length and then eventually ruptures the coleoptiles while undergoing further growths.
The ruptured plumule then grows into radical, and the root system then replaces it. In this germination, the terminal part of epicotyls is curved for reducing damage to plumule by friction due to the soil particles.
Hypogeal Germination Seed Examples
Here are some hypogeal germination examples:
Among the dicotyledons, pea, gram, and groundnut are some prominent examples.
In monocotyledons, maize, coconut, rice, and wheat are some common examples.
Pros and Cons Related to Hypogeal Germination
The benefit of hypogeal germination is that the plant or the seedlings are protected from early grazing in this process. In contrast, the disadvantage of hypogeal germination is that in this process, the plant cannot start synthesizing its food or photosynthesize until the true leaves appear entirely.
Key Points Necessary to Understand About Hypogeal Germination
Hypogeal germination is among the prominent types of germination in which the seed leaves or cotyledons stay under the soil surface during the entire germination process.
In this, the terminal part of the epicotyl stays curved for reducing the damage to the plumule due to the friction from soil particles.
In hypogeal germination, hypocotyls do not elongate more. Instead of that, the epicotyl grows while keeping the plumule above the soil.
With the elongation of the epicotyls, the plumule emerges out of the seed coat in the process.
In this germination, the energy for growth is mainly derived from the endosperm.
Epicotyl is comparatively more extended in the plants, which show hypogeal germination.
Cotyledons do not appear as playing any significant role during photosynthesis.
Plumule does not always stay enclosed and protected by the cotyledons until it emerges out of the soil.
Mostly, the monocot seeds are the ones that show hypogeal germination prominently.
Hypogeal germination occurs in several plants, including maize, arum, water lily, gram, pea, and coconut.
This is all about hypogeal germination and its examples. Understand the difference of this germination process with the rest and focus on its traits to grab hold of the concept.
FAQs on Hypogeal Germination in Flowering Plants
1. What is hypogeal germination?
Hypogeal germination is a type of seed germination in which the cotyledons remain below the soil surface. In this process:
- The epicotyl elongates and pushes the plumule upward.
- The cotyledons stay underground and often act as food storage organs.
- The first green leaves develop above the soil from the plumule.
2. How does hypogeal germination occur step by step?
Hypogeal germination occurs when the epicotyl elongates and lifts the plumule above the soil while cotyledons remain underground. The steps include:
- Seed absorbs water through imbibition.
- Enzymes activate and stored food in cotyledons is mobilized.
- The radicle emerges first to form the primary root.
- The epicotyl grows upward, forming a hook that protects the plumule.
- The plumule develops into the shoot system above the soil.
3. What is the difference between hypogeal and epigeal germination?
The main difference is that in hypogeal germination cotyledons remain below the soil, while in epigeal germination cotyledons come above the soil surface. Key differences include:
- Hypogeal: Epicotyl elongates; cotyledons stay underground (e.g., pea, maize).
- Epigeal: Hypocotyl elongates; cotyledons emerge above ground (e.g., bean, castor).
- In hypogeal type, cotyledons mainly store food; in epigeal type, they may become photosynthetic.
4. What is the role of the epicotyl in hypogeal germination?
In hypogeal germination, the epicotyl elongates and pushes the plumule above the soil surface. Its functions include:
- Forming an epicotyl hook to protect the young shoot.
- Carrying the plumule upward for exposure to light.
- Helping establish the aerial shoot system.
5. Why do cotyledons remain underground in hypogeal germination?
Cotyledons remain underground in hypogeal germination because the hypocotyl does not elongate and the epicotyl lifts only the plumule. As a result:
- Cotyledons stay protected within the soil.
- They function mainly as food storage organs.
- They are less exposed to grazing or environmental damage.
6. What are some examples of plants showing hypogeal germination?
Common examples of plants with hypogeal germination include pea (Pisum sativum), gram (Cicer arietinum), and maize (Zea mays). In these plants:
- Cotyledons remain below the soil.
- The epicotyl elongates to raise the plumule.
- The first true leaves appear above ground.
7. Is hypogeal germination more common in monocots or dicots?
Hypogeal germination occurs in both monocots and dicots, but it is very common in monocots like maize. For example:
- Monocots: Maize shows hypogeal germination.
- Dicots: Pea and gram also show hypogeal germination.
8. What is the function of cotyledons in hypogeal germination?
In hypogeal germination, the primary function of cotyledons is to store and supply nutrients to the developing seedling. Specifically:
- They contain stored starch, proteins, or fats.
- They provide energy until the seedling becomes photosynthetically active.
- They usually do not turn green or perform photosynthesis.
9. What are the advantages of hypogeal germination?
The main advantage of hypogeal germination is increased protection of cotyledons and food reserves. Benefits include:
- Cotyledons remain safe from herbivores and mechanical injury.
- Stored food remains protected underground.
- The plant can regrow shoots if the aerial part is damaged.
10. Does hypogeal germination affect early seedling growth?
Yes, hypogeal germination affects early seedling growth by keeping cotyledons underground while the shoot develops from the plumule. As a result:
- The seedling relies on stored food for a longer period.
- The first visible leaves are true leaves, not cotyledons.
- Growth above ground depends on epicotyl elongation.
