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Extraction of fibres from stinging nettles (AS)

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Laura Pearson A4.06S CORE - Extraction of 'Fibres' from Stinging Nettles Introduction In this investigation I am going to be looking at the strength of fibres taken from a stem of: (i) celery, (ii) nettle stem and the (iii) nettle its self. (i) (ii) (iii) (1) To understand the strength of the fibres I need to investigate the material they are made from. Within the fibre of the plant there are sclerenchyma, the xylem and phloem. These make up the vascular bundle and the relevant products that I am going to research are; cellulose and lignin. Cellulose Is made up of � glucose and has glycosidic bonds between the 1st and 4th carbon, however every odd molecule is rotated 180�. This increases the stability of the polysaccharide and prevents the molecule from twisting. (2) To further create more structure the glucose molecules are linked together with neighbouring molecules by hydrogen bonds to form micro fibrils. These are wound in a helical shape around the cell and stuck together with a polysaccharide known as Hemicelluloses and Pectins (3) Each individual mircofibril is wound with others to form a fibril. Lignin In order for the cell walls to be waterproof the plant produces a polymer called lignin. This impregnates the cellulose cell wall and the combination of cellulose mircofibrils and lignin give the tubes great tensile strength.(4) ...read more.


Stems of mature stinging nettles ii. Fibres form Celery iii. Fibres from nettle iv. Bowl v. Paper towels Procedure for Retting i. Remove leaves and any flowers from stems ii. Place stems in a bowl of water until completely submerged. iii. Leave for at least a week iv. Remove stems from water v. Wash to remove softened tissue and dry remaining fibres vi. The outside cuticle and epidermal layers will rub away to leave fibres Safety Considerations Eye protection and gloves need to be worn when dealing with unretted nettles to avoid being stung. (9) Hands must also be washes after handling soaked fibres. (10) When finished retting the water will be nitrogen rich and must be treated before throwing away. Equipment for investigation vi. Stems of mature stinging nettles vii. Fibres form Celery viii. Fibres from nettle i. Two clamp stands ii. Weights Method - Practical Compression i. Once fibres are collected set up two clam opposite each other and tie a knot in each end of the fibre ii. Attach to pole, making sure the fibre is taught iii. Add weights 10g at a time ensuring that the weight in the middle of the fibre iv. Record the weight when the fibre breaks Tension i. Tie two knots one in each end ii. Attach one end to the pole on the clamp stand the other to the weight holder iii. ...read more.


It would also be flexible to bend and sway in the wind and if it were lignified it would be stiffer and not be able to do so. Summary In this investigated I have found out that the degree of lignification contributes to the strength of the fibres or vascular bundle within a plant. If the lignification is significant then the fibres will be stiff, giving support and strength to hold weight in tension. If the lignification is moderate then they will provide strength by allowing the plant to be flexible this is useful when a plant leans over in the wind and the fact that it is strong in compression is a benefit too, as the plant bends, one side will be in compression. If a plant were only strong in tension it would snap at this point. These parts of the plant will not to take much weight in tension, as they are not required to take a heavy load. If lignification is poor then the fibres will still have the strength of the cellulose and some of the lignin but the main job is to remain flexible and are usually found at the top of the plant, i.e. young leaves and so are not design to take the weight of the plant. Overall it is the purpose of the particular piece of plant that decides its strength by the amount of lignin that is added. It is how many spirals and the spacing between them around the outside of the tubes that increases the weight of which it can hold. ...read more.

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