S173 Plants and People - Notes from Study Period 3 - Part 2 of 2

In part two of this study period, I'll be covering notes for cork, fibre and starch.

Cork
Anatomically it is one of the outer dead layers around a tree tunk. For commercial purposes it is taken from the cork oak (Quercus suber), which is native to western Meditteranean countries.
Recorded use is as early as the ancient Egyptians and Greeks. It has a wide range of uses such as: bottle stops, flooring material, expansion gaskets, etc.
It has a structure of honeycomb, containing air and suberin a natural wax-like substance that prevents the cork from rotting. This makes cork inert, light, and waterproof with the ability to expand and reform depending on the temperature conditions.

Cork is sustainable because the harvested tree is not cut down and is therefore able to produce new cork in future years.Each harvested tree provides enough cork to produce around 4000 bottle corks.

Fibre
Fibre is the elongated cells around the phloem that are strengthened with sclereid in the stems of plants. Fibre can also be located in wood, leaves, seed coat (as in coconuts) and in hairs attached to seeds (as in cotton). Fibre can be soft, such as flax. Others can be much hard and coarse, as with hemp.

Plant fibres are flexible, have good resistance to damage by abrasion, can withstand both heat and sunlight. They also have littl elasticiy.
Oil-based synthetic fibres such as nylon and polypropylene are stronger than even the strongest plant fibre - hemp. They are not damaged by micro-organisms, but deteriorate in bright sunlight, melt at a lower temperature than plant fibre and are not biodegradable.

Along with ropes, fibre can be used to make fishing lines, sacking, textiles, and very flexible paper for use in tea bags and banknotes. The abaca fibres is now being mixed with special thermoplastic that can be moulded into car parts - using up to 60% less energy than the creation of traditional fibreglass.

Starch
Photosynthetic sugars that are not used quickly are stored primarily as starch. The starch provides a source of stored energy for seeds during germination - enough to sustain the plant until it can photosynthesise.

As a food source we use starch from the storage tissues of plants, including tubers and seeds. For example, rice, wheat, maize, cassava and potatoes, etc. Starch can also be converted into syrup.

Non-food uses of starch include bioplastics, which are biodegradable and compostable. This type of product has received increasing interest with the rise in prices of oil. They need special digesters to fully break down. This releases methane gas, a greenhouse gas. Another concern is that growing crops for bioplastics reduces the amount of land available for food crops.

Hope you're enjoying the course - see you in sp4!