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Plant cuticle as coating onclothes

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Introduction

Cuticle in plantsThe outer parts of most of the higher plants are enveloped inside a polymeric

complex. The outer envelop is waterproof and is made up of complex mixture

of nonpolar lipids, known as waxes and biopolyesters. It is synthesized by the

epidermal cells and covers the epidermis of leaves, young shoots and otheraerial plant organs. The thickness of the layer varies with the species and the

organs. It is usually thick in the leaves and the fruits whereas for species, It is

found to be thicker in the mesophytic and aquatic plants than in xerophytes

and plants on dry lands.

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The structure of cuticleThe cuticle is the combined structure of the polyesters and the waxes on top

of it. In the 19th century, people carrying out tests on cuticle figured out that

the cuticular layer was released from the plant with the treatment from

strong acids. Later on this layer was found to be attached to the epidermalcells with the help of a pertinacious glue. This glue is known as pectin. Pectin

is also present in between the epidermal cells to fill the cracks between them.

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simplified representations of the cuticle

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Function•The main function of the cuticle is to prevent the loss of water from the

stoma and also to not let the water enter directly the plant from the

epidermis.

•The other function is the protection of the parts they cover.

It does so by

Preventing contamination of plant tissues with external water, dirt and

microorganisms

Preventing the attack from insects and animals.Reflecting UV rays and preventing the exposure of the plant to it.

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Function in aquatic plants• Since the aquatic plants grow in water, their external parts have to be

waterproof to reduce the gain of unwanted water.

• And since the plant body is either totally or partially immersed in water,

the plant could decay fast. So, the cuticles prevents the decaying of the

plant body.

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Choice of plant

We needed to make a waterproof cloth and what we thought would be the

best for it was to use the leaves of an aquatic plant. We could have used some

xerophytes for we can easily extract the cuticles from it, but the function of

the cuticle in the xerophytic plants is to reduce the transpiration and thereby

reduce the loss of water but using it would not let our skin breathe out water

vapours. Transpiration in plants is similar to the loss of water through skin in

animals and it would be uncomfortable for people to wear it. So we selected

an aquatic plant, lotus.

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History of waterproof clothes

• Waxed clothesFrom the 15th century people had started to apply fish oil to make their

clothing waterproof. Those clothes had fish-like smell and were not that good

preventing water. In 1795, Francis Webster Ltd added linseed oil to flax sails

to create more efficient sails. In the mid-1920s, three companies co-operatedto create paraffin-impregnated cotton, which produced a highly water

resistant cloth, breathable but without the stiffness in the cold or yellowing

with age. But now, modern materials have replaced it.

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• PTFE and other synthetic fibersNow a days synthetic fibers have dominated the waxed clothes. Polyamide

fibers of nylon and polymers of fluoroalkenes such as polytetrafluoroethylene

can better repel water. Due to the presence of non polar tetrafluoroethene

monomer and strong carbon-fluorine bond, it does not attract watermolecules and is less reactive to chemicals.

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Extraction

Since the cuticle is attached to the epidermis with the help of pectin, we

treated the leaf to some chemicals to disrupt the pectin layer and release the

cuticle. The most commonly used gentle methods are treatment to

ammonium oxalate/oxalic acid or some pectin degrading enzymes.

First we dissolved the epicuticular waxes using chloroform and put the leaves

inside a beaker with ammonium oxalate/ oxalic acid. We left it for about a day

but we could observe no change. And thus we exposed the leaves to strong

acid. We used zinc chloride in concentrated (about 2 mol.dm-3 ) hydrochloric

acid in the ratio of 1gram: 1.7ml. We again left it for a day and when we

looked at it again, we could see the cuticular membranes sticking out of the

leaves. We tried to separate the membranes physically but only got eithersmall fragments of it or big ones with parts of leaf on it.

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Application

The size of the cuticular membrane was not a problem for us at the

beginning. For the application of the membrane to a cloth or a cloth fiber, we

thought of dissolving the membrane in a volatile solvent and letting the fiber

soak the membrane from the solvent then coating the cloth with waxes. But

what we thought was not possible. We tried to dissolve the small fragments

of the membrane into ethyl acetate. We supposed that the membrane would

dissolve due to the interlinking of the hydrogen bonding between acetate and

the polyesters of the membrane, but it did not get dissolved.

So, the only way we could think was to glue it to the cloth, just like how it

remained in the nature.

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Depolymerization of cuticle

Since the cuticular membrane is mostly polyesters, most commonly used

methods include alkaline hydrolysis, transesterification with methanol

containing boron trifluoride or sodium methoxide or reductive cleavage by

reducing agents. We used potassium hydroxide to break the ester bond.

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Chromatography

The depolymerized cuticular membrane and the epicuticular waxes were

used for the analysis of their composition. Gas-liquid chromatrography was

done to find the composition of the membrane whereas Gas-liquid

chromatography with mass spectrometry was done for the waxes.

The following result was obtained from the chromatography.

The membrane contained mostly the C16 and C18 family.

The C16 family mainly consisted of hydroxyacids, carboxylic acids and triols;

whereas the C18 family included epoxy acids and alkenioc acids.

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The epicuticular waxes were dissolved in chloroform before the cuticle

extraction was done. So the chloroform solution was left to evaporate. The

waxes were left after the chloroform got vaporized.

• Alkanes-36%

•

Primary alcohols-23%• Alkyl esters-11%

• Triterpenoids-7%

• Unidentified wax mixture-14%

• Secondary alcohols, alkenols and benzyl esters- others

C22 to C32 primary alkohols

C12 to C22 alkyl esters

C32 to C36 benzyl esters

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Advantages

• The cuticles are naturally made polymers. So there is no need to make

them ourselves.

• It is easier to extract and apply.

• Provides a good barrier to water even with thin layer of it. (less than 15

microns)• Reflects UV radiations.

• Provides a two layered protection.

• Provides resistance to the decaying of the cloth.

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disadvantages

• The water repelling nature is not as good as that of fluorocarbons.

• It is only resistant to some of the chemicals and can be easily corroded

with organic solvents and alkaline solutions.

• The waxes get weathered as the time passes.

•The cloth gets stiffened due to the layer.

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Thank you

cuticles (1)

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