Plant cuticle

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Water beads on the waxy cuticle of kale leaves Kale2.jpg
Water beads on the waxy cuticle of kale leaves

A plant cuticle is a protecting film covering the epidermis of leaves, young shoots and other aerial plant organs without periderm. It consists of lipid and hydrocarbon polymers impregnated with wax, and is synthesized exclusively by the epidermal cells. [1]



Anatomy of a eudicot leaf Leaf Tissue Structure.svg
Anatomy of a eudicot leaf

The plant cuticle is a layer of lipid polymers impregnated with waxes that is present on the outer surfaces of the primary organs of all vascular land plants. It is also present in the sporophyte generation of hornworts, and in both sporophyte and gametophyte generations of mosses [2] The plant cuticle forms a coherent outer covering of the plant that can be isolated intact by treating plant tissue with enzymes such as pectinase and cellulase.


The cuticle is composed of an insoluble cuticular membrane impregnated by and covered with soluble waxes. Cutin, a polyester polymer composed of inter-esterified omega hydroxy acids which are cross-linked by ester and epoxide bonds, is the best-known structural component of the cuticular membrane. [3] [4] The cuticle can also contain a non-saponifiable hydrocarbon polymer known as Cutan. [5] The cuticular membrane is impregnated with cuticular waxes [6] and covered with epicuticular waxes, which are mixtures of hydrophobic aliphatic compounds, hydrocarbons with chain lengths typically in the range C16 to C36. [7]

Cuticular wax biosynthesis

Cuticular wax is known to be largely composed of compounds which derive from very-long-chain fatty acids (VLCFAs), such as aldehydes, alcohols, alkanes, ketones, and esters. [8] [9] Also present are other compounds in cuticular wax which are not VLCFA derivatives, such as terpenoids, flavonoids, and sterols, [9] and thus have different synthetic pathways than those VLCFAs.

The first step of the biosynthesis pathway for the formation of cuticular VLCFAs, occurs with the de novo biosynthesis of C16 acyl chains (palmitate) by chloroplasts in the mesophyll, [1] and concludes with the extension of these chains in the endoplasmic reticulum of epidermal cells. [9] An important catalyzer thought to be in this process is the fatty acid elongase (FAE) complex. [8] [9] [10]

To form cuticular wax components, VLCFAs are modified through either two identified pathways, an acyl reduction pathway or a decarbonylation pathway. [9] In the acyl reduction pathway, a reductase converts VLCFAs into primary alcohols, which can then be converted to wax esters through a wax synthase. [9] [10] In the decarbonylation pathway, aldehydes are produced and decarbonylated to form alkanes, and can be subsequently oxidized to form secondary alcohols and ketones. [8] [9] [10] The wax biosynthesis pathway ends with the transportation of the wax components from the endoplasmic reticulum to the epidermal surface. [9]


The primary function of the plant cuticle is as a water permeability barrier that prevents evaporation of water from the epidermal surface, and also prevents external water and solutes from entering the tissues. [11] In addition to its function as a permeability barrier for water and other molecules (prevent water loss), the micro and nano-structure of the cuticle have specialised surface properties that prevent contamination of plant tissues with external water, dirt and microorganisms. Aerial organs of many plants, such as the leaves of the sacred lotus ( Nelumbo nucifera ) have ultra-hydrophobic and self-cleaning properties that have been described by Barthlott and Neinhuis (1997). [12] The lotus effect has applications in biomimetic technical materials.

Dehydration protection provided by a maternal cuticle improves offspring fitness in the moss Funaria hygrometrica [2] and in the sporophytes of all vascular plants. In angiosperms the cuticle tends to be thicker on the top of the leaf (adaxial surface), but is not always thicker. The leaves of xerophytic plants adapted to drier climates have more equal cuticle thicknesses compared to those of mesophytic plants from wetter climates that do not have a high risk of dehydration from the under sides of their leaves.

"The waxy sheet of cuticle also functions in defense, forming a physical barrier that resists penetration by virus particles, bacterial cells, and the spores and growing filaments of fungi". [13]


The plant cuticle is one of a series of innovations, together with stomata, xylem and phloem and intercellular spaces in stem and later leaf mesophyll tissue, that plants evolved more than 450 million years ago during the transition between life in water and life on land. [11] Together, these features enabled upright plant shoots exploring aerial environments to conserve water by internalising the gas exchange surfaces, enclosing them in a waterproof membrane and providing a variable-aperture control mechanism, the stomatal guard cells, which regulate the rates of transpiration and CO2 exchange.

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Gametophyte Haploid stage in the life cycle of plants and algae

A gametophyte is one of the two alternating multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has one set of chromosomes. The gametophyte is the sexual phase in the life cycle of plants and algae. It develops sex organs that produce gametes, haploid sex cells that participate in fertilization to form a diploid zygote which has a double set of chromosomes. Cell division of the zygote results in a new diploid multicellular organism, the second stage in the life cycle known as the sporophyte. The sporophyte can produce haploid spores by meiosis that on germination produce a new generation of gametophytes.

Lipid Substance of biological origin that is soluble in nonpolar solvents

In biology and biochemistry, a lipid is a macro biomolecule that is soluble in nonpolar solvents. Non-polar solvents are typically hydrocarbons used to dissolve other naturally occurring hydrocarbon lipid molecules that do not dissolve in water, including fatty acids, waxes, sterols, fat-soluble vitamins, monoglycerides, diglycerides, triglycerides, and phospholipids.

Plant cell Type of eukaryotic cell present in green plants

Plant cells are eukaryotic cells present in green plants, photosynthetic eukaryotes of the kingdom Plantae. Their distinctive features include primary cell walls containing cellulose, hemicelluloses and pectin, the presence of plastids with the capability to perform photosynthesis and store starch, a large vacuole that regulates turgor pressure, the absence of flagella or centrioles, except in the gametes, and a unique method of cell division involving the formation of a cell plate or phragmoplast that separates the new daughter cells.

Suberin Hydrophobic lipid polyester in plant cell walls

Suberin, cutin and lignins are complex, higher plant epidermis and periderm cell-wall macromolecules, forming a protective barrier. Suberin, a complex polyester biopolymer, is lipophilic, and composed of long chain fatty acids called suberin acids, and glycerol. Suberins and lignins are considered covalently linked to lipids and carbohydrates, respectively, and lignin is covalently linked to suberin, and to a lesser extent, to cutin. Suberin is a major constituent of cork, and is named after the cork oak, Quercus suber. Its main function is as a barrier to movement of water and solutes.

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Lotus effect Self-cleaning properties

The lotus effect refers to self-cleaning properties that are a result of ultrahydrophobicity as exhibited by the leaves of Nelumbo, the lotus flower. Dirt particles are picked up by water droplets due to the micro- and nanoscopic architecture on the surface, which minimizes the droplet's adhesion to that surface. Ultrahydrophobicity and self-cleaning properties are also found in other plants, such as Tropaeolum (nasturtium), Opuntia, Alchemilla, cane, and also on the wings of certain insects.

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Epidermis (botany) Layer of cells that covers leaves, flowers, roots of plants

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Epicuticular wax is a coating of wax covering the outer surface of the plant cuticle in land plants. It may form a whitish film or bloom on leaves, fruits and other plant organs. Chemically, it consists of hydrophobic organic compounds, mainly straight-chain aliphatic hydrocarbons with or without a variety of substituted functional groups. The main functions of the epicuticular wax are to decrease surface wetting and moisture loss. Other functions include reflection of ultraviolet light, assisting in the formation of an ultrahydrophobic and self-cleaning surface and acting as an anti-climb surface.

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Wilhelm Barthlott

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  1. 1 2 Kolattukudy, PE (1996) Biosynthetic pathways of cutin and waxes, and their sensitivity to environmental stresses. In: Plant Cuticles. Ed. by G. Kerstiens, BIOS Scientific publishers Ltd., Oxford, pp 83-108
  2. 1 2 Budke, J.M.; Goffinet, B.; Jones, C.S. (2013). "Dehydration protection provided by a maternal cuticle improves offspring fitness in the moss Funaria hygrometrica". Annals of Botany. 111 (5): 781–789. doi: 10.1093/aob/mct033 . PMC   3631323 . PMID   23471009.
  3. Holloway, PJ (1982) The chemical constitution of plant cutins. In: Cutler, DF, Alvin, KL and Price, CE The Plant Cuticle. Academic Press, pp. 45-85
  4. Stark, RE and Tian, S (2006) The cutin biopolymer matrix. In: Riederer, M & Müller, C (2006) Biology of the Plant Cuticle. Blackwell Publishing
  5. Tegelaar, EW, et al. (1989) Scope and limitations of several pyrolysis methods in the structural elucidation of a macromolecular plant constituent in the leaf cuticle of Agave americana L., Journal of Analytical and Applied Pyrolysis, 15, 29-54
  6. Jetter, R, Kunst, L & Samuels, AL (2006) Composition of plant cuticular waxes. In: Riederer, M & Müller, C (2006) Biology of the Plant Cuticle. Blackwell Publishing, 145-181
  7. Baker, EA (1982) Chemistry and morphology of plant epicuticular waxes. In: Cutler, DF, Alvin, KL and Price, CE The Plant Cuticle. Academic Press, 139-165
  8. 1 2 3 Yeats, Trevor H.; Rose, Jocelyn K.C. (September 2013). "The Formation and Function of Plant Cuticles". Plant Physiology. 163 (1): 5–20. doi:10.1104/pp.113.222737. ISSN   0032-0889. PMC   3762664 . PMID   23893170.
  9. 1 2 3 4 5 6 7 8 Kunst, L; Samuels, A. L (2003-01-01). "Biosynthesis and secretion of plant cuticular wax". Progress in Lipid Research. 42 (1): 51–80. doi:10.1016/S0163-7827(02)00045-0. ISSN   0163-7827. PMID   12467640.
  10. 1 2 3 Suh, Mi Chung; Kim, Hae Jin; Kim, Hyojin; Go, Young Sam (2014-04-01). "Arabidopsis Cuticular Wax Biosynthesis Is Negatively Regulated by the DEWAX Gene Encoding an AP2/ERF-Type Transcription Factor". The Plant Cell. 26 (4): 1666–1680. doi:10.1105/tpc.114.123307. ISSN   1040-4651. PMC   4036578 . PMID   24692420.
  11. 1 2 Raven, J.A. (1977). "The evolution of vascular land plants in relation to supracellular transport processes". Advances in Botanical Research. 5: 153–219. doi:10.1016/S0065-2296(08)60361-4. ISBN   9780120059058.
  12. Barthlott, W.; Neinhuis, C (1997). "Purity of the sacred lotus, or escape from contamination in biological surfaces". Planta. 202: 1–8. doi:10.1007/s004250050096. S2CID   37872229.
  13. Freeman, S. (2002). Biological Science. New Jersey: Prentice-Hall, Inc. ISBN   978-0130819239.