Difference Between Lignin and Suberin

The key difference between lignin and suberin is that lignin is a phenolic biopolymer, whereas suberin is a polyester biopolymer.

Lignin and suberin are complex biopolymers that are present in higher plant epidermis and periderm as a structural component. Both these are important structural components in plants, mainly in higher plants.

1. Overview and Key Difference
2. What is Lignin
3. What is Suberin
4. Side by Side Comparison – Lignin vs Suberin in Tabular Form
5. Summary

What is Lignin?

Lignin is a cross-linked phenolic polymer material that forms key structural materials in the supporting tissues of plants such as vascular plants and algae. This substance is very important in the formation of cell walls in wood and bark of the tree. This is because the lignin is a very rigid compound, and it does not undergo rotting easily.

The composition of lignin in a plant can vary from one plant species to another. Compared to other biopolymers, lignin is different because it shows heterogeneity and lacks a primary structure. Lignin is relatively hydrophobic, and it is rich in aromatic subunits. However, it is difficult to measure the degree of polymerization in lignin due to the highly cross-linked structure and its heterogeneous nature.

Figure 01: Biological Functions of Lignin

Lignin can fill up the spaces in between cellulose, hemicellulose, and pectin components in cell walls. Lignin is especially present in vascular and supportive tissues in plants. Generally, lignin can be found bound to hemicellulose covalently. This cross-linking between different polysaccharides and lignin give the cell wall extra strength.

Furthermore, lignin is hydrophobic, which is very important in water transport through vascular vessels. Since most polysaccharides are hydrophilic and permeable to water, it is important to have lignin in the cell walls to cover up any leakages through the xylem vessel walls.

What is Suberin?

Suberin is a type of biopolymer which has a polyester chemical structure. It falls under the category of higher plant epidermis and periderm cell-wall macromolecules along with lignin and cutin. This substance is important in making a protective barrier. This polyester biopolymer is lipophilic, and it contains long chains of fatty acids. Due to its lipophilic nature, these macromolecules can link to the lipid and carbohydrate molecules. We can mainly find suberin in the cork of the plant. The main function of suberin in plants is to prepare a protective barrier for water and solutes.

Figure 02: Deposition of Suberin

When considering the composition of suberin, it has two major domains as polyaromatic domain and polyaliphatic domain. The polyaromatic domain is located in the primary cell wall, while the polyaliphatic domain can be found mainly in between the primary cell wall and the cell membrane.

What is the Difference Between Lignin and Suberin?

Lignin and suberin are important structural components in plants. The key difference between lignin and suberin is that lignin is a phenolic biopolymer, whereas suberin is a polyester biopolymer.

We can find lignin mainly in the bark and wood of trees while suberin is present mainly in the cork of the plant. When considering the cell structure, lignin can be found in the spaces between cellulose, hemicellulose, and pectin in the cell walls whereas suberin can be found in the primary cell wall and between the primary cell wall and cell membrane. So, this another difference between lignin and suberin.

Below infographic summarizes the differences between lignin and suberin.

Summary – Lignin vs Suberin

Lignin and suberin are biopolymers that are important as structural components in plants. The key difference between lignin and suberin is that lignin is a phenolic biopolymer, whereas suberin is a polyester biopolymer.

Reference:

1. “Lignin.” Wikipedia. Wikimedia Foundation, 19 Apr. 2020. Web. 26 June 2020.

Image Courtesy:

1. “Lignin Polymerisation” By User:Chino – Own work (Public Domain) via Commons Wikimedia
2. “Deposition-of-suberin-lamellae-in-endodermis-of-two-rice-genotypes-roots” By M. R. Momayezi, A. R. Zaharah, M. M. Hanafi – M. R. Momayezi et. al. “The Effects of Cation Ratios on Root Lamella Suberization in Rice ( Oryza sativa L.) with Contrasting Salt Tolerance”, International Journal of Agronomy doi:10.1155/2012/769196 (CC BY 4.0) via Commons Wikimedia