Difference between periderm, bark and rhytidome

Peridermis, bark and rhytidome are terms used in botany that refer to the covering of the plant's body.. However, despite what many people think, these three words should not be used interchangeably. Find out below the difference between them.

→ periderm

periderm is the name given to the set of lining tissues that appear in plants with thick growth (secondary growth), replacing the epidermis. The peridermis, unlike the epidermis, is not a single tissue, being formed by the suber, phelogen and feloderm.

• Suber: The suber is the outermost tissue and has dead cells at maturity with a large amount of suberin (a fatty substance). It is a fabric with a very compact and waterproof cell arrangement.

• phelogen: Phelogen is a meristematic tissue that forms the suberum externally and the pheloderm internally.

• Feloderm: Feloderm is a tissue formed by parenchymal cellsat active cells that resemble cortical parenchyma cells.

→ bark

The bark is often used to refer to the periderm or even just the suber. Although,

the bark, which is not a technical term, refers to tissues that are located outside the vascular cambium. Therefore, it corresponds to a series of tissues that include the peridermis and other tissues, which can be of secondary or primary origin.

The shell can also be divided into outer shell and inner shell. The outer shell corresponds to the dead part, and the inner shell refers to the living part. The inner shell is, therefore, the part located internally to the innermost phelogen up to the vascular cambium. We speak of a more internal phelogen because, in some species, parenchymal cells can become meristematic and form a new phelogen.

→ rhytidome

The term rhytidome is used to refer to the set of dead tissues that are located outside the last periderm that was formed. Therefore, rhytidome can be used as a synonym for the outer shell, but it cannot be considered a synonym for the general term “shell”.
By Ma. Vanessa Sardinha dos Santos

Source: Brazil School - https://brasilescola.uol.com.br/biologia/diferenca-entre-periderme-casca-ritidoma.htm