What is the Difference Between Sporopollenin and Cuticle

The key difference between sporopollenin and cuticle is that sporopollenin is a lipid and phenolic based polymer present in the tough outer walls of plant spores and pollen grains of land plants, while cuticle is a continuous lipophilic polymer that is coating the aerial surfaces of land plants.

Plants have three major extracellular hydrophobic barriers. They are cuticle, sporopollenin, and suberin. These extracellular barriers commonly consist of lipids. The main function of these layers is protecting plants against various environmental stresses such as salinity, water deficit, pathogen attack and wounding.

1. Overview and Key Difference
2. What is Sporopollenin
3. What is Cuticle
4. Similarities – Sporopollenin and Cuticle
5. Sporopollenin vs Cuticle in Tabular Form
6. Summary

What is Sporopollenin?

Sporopollenin is a lipid and phenolic based polymer present in the tough outer walls of plant spores and pollen grains of land plants. It is one of the most chemically inert biological polymers. It is also chemically well stable. It is well preserved in soils and sediments. Sometimes, sporopollenin is also found in the cell walls of green alga. Normally, spores are dispersed in different ways, such as wind, water, and animals. If the conditions are suitable, the walls of pollen grains and spores that impregnate sporopollenin can persist in the fossils for more than a hundred million years. This is because sporopollenin is resistant to chemical degradation by organic and inorganic chemicals.

Figure 01: Pollen Grains

Analytical techniques have revealed that sporopollenin is a complex biopolymer. It typically contains long-chain fatty acids, phenylpropanoids, phenolics and traces of carotenoids within a random copolymer. It believes sporopollenin drives from several precursors that are cross-linked to produce a rigid structure. Furthermore, tapetal cells are involved in the biosynthesis of sporopollenin. These cells have a secretory system containing lipophilic globules. Moreover, the main function of sporopollenin is to protect pollen grains from external damages such as rain and high temperature.

What is Cuticle?

A cuticle is a continuous lipophilic layer that is coating the aerial surfaces of land plants. The plant cuticle is a protective covering. It covers the epidermis of leaves, young shoots, and other aerial plant organs without periderm. Plant cuticle consists of lipids and hydrocarbon polymers impregnated with wax. The cuticle is chemically made up of waxes embedded within and overlaying a matrix of cutin. Waxes are mainly derivatives of long-chain fatty acids (C20-C34), which include aldehydes, alkanes, primary alcohol, secondary alcohol, ketones, and esters. Cutin is an esterified polymer of C16 and C18 omega and mid-chain hydroxy fatty acid that is esterified to glycerol skeleton.

Figure 02: Cuticle

It is usually synthesized from epidermal cells. Cuticles are normally present on the outer surfaces of the primary organs of all vascular land plants. But sometimes, it is also present in the sporophyte generation of hornworts and both sporophyte and gametophyte generations of mosses. A cuticle can be isolated by treating plant tissue with enzymes such as pectinase and cellulase.

What are the Similarities Between Sporopollenin and Cuticle?

Sporopollenin and cuticle are two major extracellular hydrophobic barriers in the land plants.
Both are complex biopolymers.
These layers contain lipids.
These layers protect plants against various environmental stresses such as salinity, water deficit, pathogen attack and wounding.

What is the Difference Between Sporopollenin and Cuticle?

Sporopollenin is a lipid and phenolic based polymer present in the tough outer walls of plant spores and pollen grains of land plants, while the cuticle is a continuous lipophilic polymer that is coating the aerial surfaces of land plants. So, this is the key difference between sporopollenin and cuticle. Furthermore, sporopollenin typically contains long-chain fatty acids, phenylpropanoids, phenolics, and traces of carotenoids within a random copolymer. Meanwhile, a cuticle typically consists of waxes embedded within and overlaying a matrix of cutin esterified polymer.

The following infographic lists the differences between sporopollenin and cuticle in tabular form for side by side comparison.

Summary – Sporopollenin vs Cuticle

Plants have three major extracellular hydrophobic barriers or layers such as cuticle, sporopollenin, and suberin for protection. Sporopollenin is a lipid and phenolic based polymer present in the tough outer walls of plant spores and pollen grains of land plants, while the cuticle is a continuous lipophilic polymer that is coating the aerial surfaces of land plants. Thus, this is the summary of the difference between sporopollenin and cuticle.

Reference:

1. “Sporopollenin: Distribution, Production and Functions.” Biology Discussion.
2. “Plant Cuticle.” An Overview | ScienceDirect Topics.

Image Courtesy:

1. “Misc pollen” By Dartmouth College Electron Microscope Facility – Dartmouth College Electron Microscope Facility (Public Domain) via Commons Wikimedia
2. “Leaf Tissue Structure” By Zephyris – Own work (CC BY-SA 3.0) via Commons Wikimedia