Explain functions of cuticle?

Answer 1

PLANT CUTICLE


Plant cuticles are a protective waxy covering produced only by the epidermal cells of leaves, young shoots and all other aerial plant organs.

The cuticle tends to be thicker on the top of the leaf, but is not always thicker in plants living in dry climates than in those from wet climates, despite the persistent myth.

The cuticle is composed of an insoluble cuticular membrane impregnated by and covered with soluble waxes. Cutin, a polyester polymer composed of inter-esterified straight-chain hydroxy acids which are cross-linked by ester and epoxide bonds, is the best-known structural component of the cuticular membrane

The cuticle can also contain a non-saponifiable hydrocarbon polymer known as Cutan .

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 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 .

Together, these features enabled 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 could regulate the rates of H2O evaporation and CO2 exchange.

In addition to its function as a permeability barrier for water and other molecules, the micro and nano-structure of the cuticle confer specialised surface properties that prevent contamination of plant tissues with external water, dirt and microorganisms. Many plants, such as the leaves of the sacred lotus (Nelumbo nucifera) exhibit ultra-hydrophobic and self-cleaning properties . The lotus effect has potential uses in biomimetic technical materials.

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



ANIMAL CUTICLE

In Zoology the invertebrate cuticula is a multi-layered structure outside of epidermis of many invertebrates, notably roundworms and arthropods, where it forms an exoskeleton. It is formed by fatty acids with alcohols other than glycerol.

In human anatomy, the cuticle refers to the fold of skin at the proximal end of the fingernail; see eponychium.

Answer 2

"Cuticle – waxy layer on the covering the epidermis; holds in moisture, prevents too much absorption of water."

http://www.salem.k12.va.us/staff/jwright/LeafParts.htm