Suberin

Contributions from the Botanical Laboratory, vol. 12 (1934) (20065769024)

Suberin is a complex polymer found in the cell walls of certain plant cells, where it serves as a barrier to water and solute movement. It is a key component in the protective layers of bark and the cork of cork oak trees, as well as in the Casparian strip in roots. Suberin is a heterogeneous substance, composed of fatty acids, fatty alcohols, glycerol, and phenolic compounds, which are cross-linked in a manner that is not fully understood. This composition contributes to its function as a physical and chemical barrier, protecting plants from pathogens, preventing water loss, and regulating the movement of nutrients and water.

Structure and Composition

Suberin is primarily found in the outer layers of plants, such as the periderm, which includes the cork layer, and in the endodermis of roots. Its structure is complex, consisting of an aliphatic domain and an aromatic domain. The aliphatic domain is made up of long-chain fatty acids and alcohols, while the aromatic domain contains phenolics such as ferulic acid and coumaric acid. These components are polymerized through ester and ether linkages, forming a network that is both hydrophobic and chemically resistant.

Function

The primary function of suberin is to act as a barrier. In the roots, the Casparian strip, which contains suberin, prevents the passive flow of water and solutes into the vascular system, ensuring that all nutrients undergo selective uptake. In the aerial parts of the plant, suberin in the bark and cork layers protects against physical damage, dehydration, and invasion by pathogens. Additionally, suberin plays a role in wound healing, sealing off damaged areas to prevent infection and water loss.

Biosynthesis

The biosynthesis of suberin involves several steps, starting with the synthesis of its aliphatic and aromatic components. Enzymes such as fatty acid hydroxylases, peroxidases, and cytochrome P450s are involved in the modification of fatty acids and phenolics, which are then polymerized to form suberin. The regulation of suberin biosynthesis is complex and is influenced by environmental factors such as stress, injury, and developmental cues.

Ecological and Economic Importance

Suberin not only plays a critical role in plant defense and water regulation but also has ecological and economic significance. Cork, which is rich in suberin, is harvested from the cork oak (Quercus suber) for various uses, including wine stoppers, flooring, and insulation, due to its durability, resilience, and insulating properties. Additionally, understanding the role of suberin in root water uptake and pathogen resistance has implications for agriculture, particularly in the development of crops that are more resistant to drought and disease.

Research and Applications

Research into suberin and its biosynthesis is ongoing, with potential applications in biotechnology and agriculture. Genetic engineering to modify suberin content and composition in plants could lead to crops with improved resistance to environmental stresses, enhanced water-use efficiency, and increased protection against soil-borne diseases. Furthermore, the biodegradability and chemical properties of suberin make it a material of interest for developing sustainable biomaterials and coatings.