What is the Difference Between Embryo and Endosperm

The main difference between embryo and endosperm is that the embryo is the conceptus of fertilization whereas the endosperm is the nutritive tissue of the seed. Furthermore, the fusion of the egg cell with a sperm results in an embryo while the fusion of a sperm with the binucleate central cell results in an endosperm. Moreover, the embryo is diploid while endosperm is triploid. 

Embryo and endosperm are two types of structures found in the seed of angiosperms. They occur in a process called double fertilization.  

Key Areas Covered 

1. What is Embryo
     – Definition, Formation, Function
2. What is Endosperm
     – Definition, Formation, Function
3. What are the Similarities Between Embryo and Endosperm
     – Outline of Common Features
4. What is the Difference Between Embryo and Endosperm
     – Comparison of Key Differences

Key Terms 

Angiosperm’s Seed, Double Fertilization, Endosperm, Embryo, Triple Fusion

What is Embryo 

An embryo refers to an early stage of development of a multicellular diploid eukaryotic organism.  Embryos occur in every form of multicellular organisms that undergo sexual fertilization. In seed plants like angiosperms and gymnosperms, embryo occurs inside the seed. Dicot embryo contains two cotyledons while monocot embryo contains a single cotyledon. The embryo in plants develops into the stem, root, and leaves. The formation of the embryo in angiosperms is known as double fertilization; here, one sperm cell in the pollen tube fuses with the egg cell, forming the embryo, while the second sperm cell fuses with the central cell of the embryo sac to form the endosperm. 

Figure 1: Double Fertilization

Moreover, embryo occurs in animals as the early stage of the development of multicellular, diploid organisms. Here, the fusion of a sperm cell and an egg cell forms the zygote, which then undergoes a series of mitotic cell divisions and cell differentiation processes in order to develop into a multicellular organism. 

What is Endosperm 

Endosperm is the nutritive tissue in the seed of angiosperms. It develops from the primary endosperm nucleus. The primary endosperm nucleus is a result of the fusion of one of the sperm nuclei with the binucleate central cell, which occurs in the embryo sac (the female gametophyte). This process is known as triple fusion since it forms a triploid cell. Furthermore, triple fusion occurs only in angiosperms. Then, the repeated mitotic cell divisions result in the endosperm. However, the ploidy of endosperms can vary from 2n to 15n.  

Figure 2: Embryo (Blue) and Endosperm (White) of Rice

The main function of the endosperm is to store the nutrients needed for the future development of the embryo. Starch is the main form of nutrients stored in the endosperm. Some endosperms store oils and proteins as well. Furthermore, the seeds with endosperms are endospermic seeds while the seeds without endosperms are non-endospermic seeds. In addition, the endosperms of dicots are known as exalbuminous since the nutrients of their endosperm are absorbed by the two cotyledons before seedling. Meanwhile, monocots contain a prominent endosperm, and their endosperm is known as albuminous. Therefore, the endosperms of monocots are often used as food.  

Similarities Between Embryo and Endosperm 

• Embryo and endosperm are two types of structures that occur in the seed of angiosperms. 
• Both occur in a process called double fertilization.  
• Also, in both, the two sperm nuclei in the pollen tube are responsible for their formation. 

Difference Between Embryo and Endosperm 

Definition 

An embryo refers to an early stage of development of a multicellular diploid eukaryotic organism while an endosperm refers to the part of a seed, which acts as a food store for the developing plant embryo, usually containing starch with protein and other nutrients. Thus, this is the main difference between embryo and endosperm.

Found in 

Also, embryo occurs in every multicellular organism that undergoes fertilization during their sexual reproduction while endosperm occurs in angiosperms. 

Formation 

Another difference between embryo and endosperm is that the embryo occurs by a process called fertilization while the endosperm occurs in a process called triple fusion.  

Types of Cells Involved in 

Moreover, fusion of a sperm and an egg cell forms an embryo while the fusion of the binucleate central cell with a sperm cell forms the endosperm. 

Ploidy 

One other difference between embryo and endosperm is that the embryo is diploid while endosperm is triploid. 

Function in Angiosperms 

Furthermore, function in angiosperms is another difference between embryo and endosperm. Embryo develops into a new individual of the species while endosperm provides nutrients to the developing embryo. 

Conclusion 

Embryo is the conceptus of fertilization in all multicellular organisms that undergo sexual reproduction. It occurs by the fusion of a sperm and egg cell. On the other hand, endosperm in the seed of angiosperms and is a result of the triple fusion in which a sperm fuses with the binucleate central cell of the embryo sac. Therefore, it is triploid. Moreover, it provides nutrients to the developing embryo. Thus, the main difference between embryo and endosperm is their purpose in the seed of angiosperms.   

References:

1. Lafon-Placette, Clément, and Claudia Köhler. “Embryo and Endosperm, Partners in Seed Development.” Current Opinion in Plant Biology, vol. 17, 2014, pp. 64–69., doi:10.1016/j.pbi.2013.11.008.

Image Courtesy:

1. “Double Fertilization” By The original uploader was Triploid at English Wikipedia. – Transferred from en.wikipedia to Commons. (CC BY 3.0) via Commons Wikimedia  
2. “Rice embryo” By Richard Jefferson’s Center for the Application of Molecular Biology to International Agriculture (CAMBIA) – BioForge.net (CC BY-SA 2.5) via Commons Wikimedia