What is the Difference Between Axile and Parietal Placentation

The main difference between axile and parietal placentation is that axile placentation is the presence of a multilocular ovary, whereas parietal placentation is the presence of a unilocular ovary.

Axile and parietal placentation are two placentation types. Placentation is the attachment of ovules inside the ovary.  

Key Areas Covered

1. What is Ovary
– Definition, Structure, Function
1. What is Axile Placentation
– Definition, Facts, Examples
2. What is Parietal Placentation
– Definition, Facts, Examples
3. Similarities Between Axile and Parietal Placentation
– Outline of Common Features
4. Difference Between Axile and Parietal Placentation
– Comparison of Key Differences

Key Terms 

Axile Placentation, Parietal Placentation

What is Ovary

In flowering plants, the ovary is a component of the female reproductive organs. It occurs at the base of the petals. Also, it contains ovules. And, above the ovary, style and stigma occur. Through them, the pollen grain grows down and on which the pollen grain lands. It fertilizes the ovule. One to many ovules occurs in an ovary, depending on the species. The ovule has three structural parts: integuments, nucellus, and embryo sac. Integuments are the two layers that cover the internal structures of the ovule. The small opening in the integuments is called the micropyle, through which the pollen tube enters the ovule. The nutrients required for embryo development are stored in the nucellus. The embryo sac cell near the microphyte develops into the egg cell. Upon fertilization, the ovule develops into a seed. 

Furthermore, fruit is the ripened ovary, resulting from the double fertilization of angiosperms. Double fertilization of the ovules in gymnosperms produces naked seeds. 

What is Axile Placentation

Axile placentation is the presence of septa that divide the ovary into two or more locules. Therefore, it contains a multilocular ovary. Meanwhile, the ovules occur along the central axis formed by the inner angle of the septa. Here, fused carpels form the septa. Examples of axile placentation include lily, hibiscus, lemon, and tomato.

Figure 1: Axile Placentation

What is Parietal Placentation

Parietal placentation is the presence of an unilocular ovary. Therefore, no septa occur inside the ovary. Importantly, ovules are attached to the ovary’s wall in parietal placentation. It occurs in cucumber.

Figure 2: Parietal Placentation

Similarities Between Axile and Parietal Placentation

• Axile and parietal placentation are two placentation types in plants.
• They are the different arrangements of ovules inside the ovary.

Difference Between Axile and Parietal Placentation

Definition

Axile placentation refers to a type of ovule arrangement in which the ovules arise from placental tissue derived from the apices of the septa of a locule. Meanwhile, parietal placentation refers to a type of placentation found in the compound, unilocular ovaries in which the ovules arise from placentae inserted on the wall of the locule near the sutures. 

Septa

Septa occur in axile placentation, while septa are absent in parietal placentation.  

Locules

Axile placentation contains a multilocular ovary, while parietal placentation contains a monolocular ovary.

Ovules

Ovules occur along the central axis formed by the inner angle of the septa in axile placentation, while ovules are attached to the ovary’s wall in parietal placentation. 

Examples

Axile placentation occurs in hibiscus, tomato, lemon, and lily, while parietal placentation occurs in cucumber. 

Conclusion

In brief, axile and parietal placentation are two arrangements of ovules in the ovary. Axile placentation contains septa that separate the ovary into locules. Therefore, it contains a multilocular ovary. Ovules occur attached to the inner angle formed by the septa in axile placentation. Examples of axile placentation include hibiscus, lemon, tomato, and lily. In comparison, parietal placentation is the presence of a unilocular ovary that is not separated by septa. Ovules occur attached to the wall of the ovary in parietal placentation. It occurs in cucumber. Therefore, the main difference between axile and parietal placentation is the presence of septa.  

References:

1. Wikimedia Foundation. (2022c, September 11). Placentation. Wikipedia. https://en.wikipedia.org/wiki/Placentation

Image Courtesy:

1. “Gynoecium morphology placentation axile-2 cross section” By Michael G. Simpson – Own work (Public Domain) via Commons Wikimedia
2. “Gynoecium morphology placentation parietal-1 cross section” By Michael G. Simpson – Own Work (Public Domain) via Commons Wikimedia