Epidermis: Outer Cell Layer of the Plant


The epidermis is the protective outer layer of clonally related cells covering all plant organs. It is composed of a number of specialised cell types which differentiate from the basal epidermal cell in adaptively significant frequencies and patterns. The epidermis is unique in developing solely through anticlinal divisions, generating a sheet of cells overlying the rest of the plant. This sheet is connected physically and biochemically to the cell layers below, with information exchange occurring in both directions. The specialised cell types within the epidermis develop either through communication among themselves, or, in some cases, through communication also with the underlying cell layers. Brief descriptions of the molecular genetic control of trichomes, stomata, root hairs and petal conical‐papillate epidermal cells are provided here, along with a summary of the role of the cuticle in epidermal cell morphology and of the interplay between cuticle regulation and cell morphology.

Key Concepts

  • The plant epidermis is a single layer of clonally related cells.
  • Plant epidermis fulfils a basic protective function, but specialised cells within the epidermis have specific roles.
  • The seedling epidermis arises by isolation of the outer layer during embryogenesis. The aerial epidermis and the root epidermis originate later, in the shoot apical meristem and in the root apical meristem, respectively.
  • Stomatal guard cells allow gas exchange, and their patterning is controlled by cell‐lineage‐based developmental mechanisms.
  • Trichomes protect the plant from herbivores, and their patterning is controlled by cell–cell interactions.
  • Root hairs increase surface area for water and nutrient uptake, and are patterned according to positional signals.
  • The cuticle overlying the epidermis can contribute to epidermal cell shape and function.
  • There is interplay between the regulation of epidermal cell shape and the regulation of cuticle production.

Keywords: trichomes; stomata; differentiation; development; patterning; root hairs; cuticle

Figure 1. (a) Adaxial epidermis of tobacco leaf showing spacing of stomatal guard cells, two different types of trichome and pavement cells. (b) Adaxial epidermis of rose petal. All cells adopt the conical‐papillate form, with heavy cuticular striations. (c) Arabidopsis root epidermis with root hairs. (d) Arabidopsis leaves with branched trichomes.
Figure 2. Epidermal cell layers. (a) The epidermis of the shoot is derived from the L1 layer of the shoot apical meristem. Communication between different cell types in the epidermis determines their patterning. (b) The epidermis of the root is derived from a set of initials in the root apical meristem. Communication between cells within the epidermis, and signals from the cortical cells below, determine cellular differentiation. (c) The protoderm covering the embryo is formed by positional isolation (signified by the red line) from the cell layers below.
Figure 3. The cuticle can be folded to form (a) stellate patterns, (b) striations parallel to the long axis of the cell or (c) more disorganised ridges. The cuticle can also (d) remain smooth, (e) form papillae or (f) be covered by epicuticular wax crystals. The mechanisms controlling epidermal cell specification can also influence the development of the cuticle and, reciprocally, the genes controlling cuticle formation and synthesis of its main components (cutin and waxes) can also impact the (g) growth and specialisation of epidermal cells.


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Further Reading

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Martin C and Glover BJ (2007) Functional aspects of cell patterning in aerial epidermis. Current Opinion in Plant Biology 10: 70–82.

Pesch M and Hulskamp M (2009) One, two, three…models for trichome patterning in Arabidopsis. Current Opinion in Plant Biology 12: 580–586.

Serna L and Martin C (2006) Trichomes: different regulatory networks lead to convergent structures. Trends in Plant Science 11: 274–280.

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Glover, Beverley J, Airoldi, Chiara A, and Moyroud, Edwige(Feb 2016) Epidermis: Outer Cell Layer of the Plant. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0002072.pub3]