The cuticle of a plant is the waxy film or membrane that covers the leaves and other dermal tissues of the plant.
The cuticle of a plant is the waxy film or membrane that covers the leaves and other dermal tissues in the aerial sections of the plant. Waxes and polymers such as cutin and cutan, which contain omega-hydroxy acids, esters, epoxides, and hydrophobic aliphatic compounds, form the cuticle. Cutin is a polyester polymer while cutan is a hydrocarbon polymer; both contribute to the plant’s ability to thrive in an aerial environment. Cuticular membranes protect plants primarily from water loss, but they also assist in other functions of dermal tissue, such as infection prevention.
In fact, a plant’s cuticle functions like human skin in that it protects the plant against excessive water loss, as well as serving as a barrier against certain bacteria, fungi, and other harmful organisms. Its film covers the top and bottom of leaves and other dermal areas of the plant, encapsulating the upper epidermal layer of plant tissue. The upper part of the leaves tend to have a thicker cuticle than the buds or the lower part of the leaves, since the upper part of the leaf is more exposed to sun, wind and pests than other dermal tissues.
Beneath the protective layer of the cuticle resides the upper and lower epidermis of the plant, as well as the mesophyll, where plant cells convert light into energy during photosynthesis. Without the plant cuticle, the water-absorbing process necessary to complete photosynthesis would require a much larger supply of water to compensate for evaporation. Fewer tender plants and young shoots would form, and even fewer would survive without the cuticle providing additional protection against bacterial or other microscopic infections.
As part of a plant’s shoot system, the components of the plant that appear above the soil line, dermal tissue is made up of dense cells known as epidermal cells. Epidermal cells are responsible for secreting the waxy polymers and other substances that make up the plant cuticle and help the plant retain water. Waxes and soluble polymers secreted by epidermal cells spread over the surface of leaves and shoots to form the protective membrane of the cuticle as these plant parts develop and grow.
Not all plants produce a cuticle. Plants with periderms, the epidermal layering system of woody plants more commonly known as bark, lack a plant cuticle. Instead, these plants have living layers of the inner periderm, such as the phelloderm and bark, as well as dead outer layers of the periderm, known as the rhytidome or cork. Woody plants such as trees, certain types of vines, and shrubs have periderm layers instead of cuticular membranes.