Making Use of Plants Flashcards
What are four examples of how humans use plants?
Clothing, rope, floor coverings and paper
What three properties do plant fibres have that make them useful?
They are long and thin, flexible, and strong
What is extraction of plant fibres also known as?
Retting
How are plant fibres retted mechanically?
By pulling out the fibres using a machine
How are plant fibres retted using chemical and enzyme digestion?
Cellulose is resistant whilst polysaccharides that hold the fibre together can be dissolved
How are plant fibres retted using caustic alkali?
To produce fibre pulps from trees, caustic alkali is needed
How are plant fibres retted using traditional heaps?
Stems are piled in heaps, allowing bacteria and fungi to naturally break down the fibres
What are mats of fibres used to absorb?
Heavy metals and also hydrocarbons from polluted water
What are biocomposites?
Plant fibres that are added to other materials
What is an example of a biocomposite?
Rapeseed fibres mixed with plastic
What are the advantages of biocomposites?
They are strong, renewable, more biodegradable and can be easier and safer to handle than artificial fibres
Plants have developed adaptations that provide ? ? to repel or even kill animals that feed on them
Chemical defences
How can a chemical prevent a plant being eaten?
A chemical that is distasteful or toxic is produced. If the animal takes a bite the taste is offensive and the animal is deterred from feeding further. If its chemical kills the predator the plant will avoid further attacks
How do the tannins in tea prevent insect attack?
They are bitter and ‘gum up’ the mouthparts of aphids
Why are pyrethrum plants so special?
They have no known pests or diseases
What chemicals do pyrethrum plants contain?
Pyrethrins
What are the chemicals in pyrethrum plants used for?
Insecticides, sprays for fruit and flowers, flea treatment and the reduction in tick infestation in cattle
What advantaged do the pyrethrum chemicals have?
They are unstable after spraying and rapidly decompose to harmless residues