In angiosperms the cuticle tends to be thicker on the top of the leaf ( adaxial surface), but is not always thicker. The lotus effect has applications in biomimetic technical materials.ĭehydration protection provided by a maternal cuticle improves offspring fitness in the moss Funaria hygrometrica and in the sporophytes of all vascular plants. 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). 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. 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. The wax biosynthesis pathway ends with the transportation of the wax components from the endoplasmic reticulum to the epidermal surface. In the decarbonylation pathway, aldehydes are produced and decarbonylated to form alkanes, and can be subsequently oxidized to form secondary alcohols and ketones. In the acyl reduction pathway, a reductase converts VLCFAs into primary alcohols, which can then be converted to wax esters through a wax synthase. To form cuticular wax components, VLCFAs are modified through either two identified pathways, an acyl reduction pathway or a decarbonylation pathway.
An important catalyzer thought to be in this process is the fatty acid elongase (FAE) complex. 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, and concludes with the extension of these chains in the endoplasmic reticulum of epidermal cells. Also present are other compounds in cuticular wax which are not VLCFA derivatives, such as terpenoids, flavonoids, and sterols, and thus have different synthetic pathways than those VLCFAs. Cuticular wax biosynthesis Ĭuticular 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. The cuticular membrane is impregnated with cuticular waxes and covered with epicuticular waxes, which are mixtures of hydrophobic aliphatic compounds, hydrocarbons with chain lengths typically in the range C16 to C36. The cuticle can also contain a non-saponifiable hydrocarbon polymer known as Cutan. 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.
The cuticle is composed of an insoluble cuticular membrane impregnated by and covered with soluble waxes.
It is also present in the sporophyte generation of hornworts, and in both sporophyte and gametophyte generations of mosses 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 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.
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