Differences Between Perisperm and Endosperm: Plant seeds include two primary tissues: Perisperm and Endosperm, which store sustenance for growing embryos. While both perform this crucial role, there is a significant variation in their origin and chromosomal composition. Most seeds include endosperm, which arises from a unique triple fusion event, resulting in triploid tissue. Perisperm, on the other hand, grows only from the seed's nucleus and is diploid. This contrast is further accentuated in plant groups such as Caryophyllaceae, where perisperm coexists with endosperm, giving extra nutrients to the embryo.
Difference Between Perisperm and Endosperm
Perisperm and endosperm are both nutritive tissues found in seeds of flowering plants (angiosperms). They serve to nourish the developing embryo, providing it with the necessary nutrients for germination and early growth. While they have similarities in function, there are several key differences between them:
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|
Feature |
Endosperm |
Perisperm |
|
Origin |
Derived from the fusion of a sperm nucleus with two polar nuclei within the embryo sac. |
Derived from the nucellus or integument tissue outside the embryo sac. |
|
Formation |
Formed after double fertilization, specifically as a result of the fusion of a sperm cell with the central cell. |
Formed before fertilization from maternal tissue. |
|
Composition |
Rich in starch, proteins, and other nutrients. |
Composition can vary but often contains storage reserves like starch, oils, and proteins. |
|
Persistence |
Often persists in the mature seed. |
May or may not persist in the mature seed, depending on the species. |
|
Function |
Primarily serves as a nutritive tissue for the developing embryo. |
Also functions as a nutritive tissue, but its exact role can vary among different plant species. |
|
Location |
Located within the embryo sac, surrounding the embryo. |
Located outside the embryo sac, surrounding the embryo. |
|
Cellular Organization |
Typically triploid (3n) due to the fusion of a haploid sperm cell with two haploid polar nuclei. |
Can be haploid (1n), diploid (2n), or triploid (3n), depending on the plant species. |
|
Development |
Develops during embryogenesis. |
Develops before fertilization and persists in some species. |
|
Size |
Can vary in size but often occupies a significant portion of the seed. |
Generally smaller in size compared to endosperm. |
|
Evolutionary Significance |
Evolved as an adaptation to provide nutrients to the developing embryo, increasing the chances of successful seed germination and seedling establishment. |
May represent an evolutionary precursor to endosperm, with some plant lineages retaining perisperm as the primary nutritive tissue in seeds. |
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What is Perisperm?
Perisperm is a food-storing tissue that emerges from the nucellus, the centre tissue of the ovule (the structure that develops into a seed). It is diploid, which means it contains two sets of chromosomes—one from each parent. Perisperm is exclusively present in a few plant groups, such as black pepper and coffee.
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Key Features of Perisperm:
- It grows from the nucellus, the tissue that surrounds the ovule inside the ovary.
- Contains nutrients for the growing seed, principally carbohydrates and proteins.
- Found in various dicotyledonous (flowering plants with two seed leaves) seeds, such as coffee, black pepper, and castor beans.
- Frequently destroyed or absorbed by the developing embryo as the seed grows, leaving little or no trace in the mature seed.
What is Endosperm?
Endosperm is another type of food-storing tissue that forms when three nuclei fuse: one sperm nucleus and two polar nuclei from the embryo sac's core cell. This process, known as triple fusion, causes the endosperm to become triploid, meaning it has three sets of chromosomes. Endosperm is more prevalent than perisperm and may be found in seeds such as wheat, maize or rice.
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Key Features of Endosperm:
- It is formed when a sperm nucleus fuses with two nuclei from the ovule's central cell.
- Most seeds are the principal source of nutrition for the growing embryo. Stores a multitude of nutrients, including carbohydrates, proteins, oils, and sugars.
- Most angiosperms (flowering plants) include seeds, which include cereals (wheat, rice, maize), legumes (peas, beans), and nuts (walnuts, almonds).
- Can be plentiful in mature seeds, supplying nutrients to developing seedlings.
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Similarities Between Perisperm and Endosperm
- Perisperm and endosperm. Both tissues function as storage organs, delivering nutrients to the growing foetus.
- They are both essential for seed growth and germination, ensuring that the embryo's basic nutritional requirements are satisfied.
- Both may include reserves such as carbohydrates, lipids, and proteins, which are necessary for embryo development.
- Both tissues are of maternal origin, having developed from ovule maternal tissues.
- Both are essential for seed germination and early seedling growth, since they provide the energy and nutrients required by the seedling to begin photosynthesis.
Perisperm and endosperm, while both acting as food storage tissues in seeds, have different origins and properties. The fundamental distinction between them is their genetic composition. Perisperm is a diploid tissue that develops straight from the nucleus of the mother plant. Endosperm, on the other hand, is triploid and is created when a sperm cell fuses with the two polar nuclei in the ovule's core cell. This variation in origin also affects their presence in mature seeds. Perisperm, a remnant of the nucellus tissue, is frequently devoured by the developing embryo, although the endosperm is the principal source of nutrients for germination in most seeds. Coffee and black pepper are examples of plants having perisperm, but grains like wheat and rice rely only on endosperm for nourishment.