Cross Section of Wood – Laxmi

The bark of the tree is the outermost layer of the tree and will protect the tree from drying out or any damage caused by the wildlife (insects, birds, etc.) The bark protect the phloem of the tree, if the bark is removed of the tree then the tree could potentially die. The bark of this tree is smooth, which shows that they tree must have been quite young as bark does not grow, but splits in order for the tree to grow in diameter. The pith of the tree section is slightly off-centre; this could have been due to the amount of sunlight that that side of the tree was receiving.
The rings of the cross section represent the age of the tree, in the cross section above it is possible to see the very light rings. The rings that are lighter grown in spring due to growth of large cells, this means the darker rings are summer because of the increase in cell growth. We can link this to why trees grow more in the summer; there is no/less winter growth due to limiting factors.
The medullary rays can originate from the cambial cells and these are secondary rays, however from this picture it is not possible to tell if it is a secondary ay or new ray. Also, when a ray starts to grow it will invariably grow through all the growth rings. Outside the cambium, the ray will be continued in the phloem, this means that each ray will have xylem and a phloem portion. (Mishra, 2009 p.146).

References:
Mishra, S. (2009) Understanding Plant Anatomy. Delhi: Discovery Publishing House.

Dye – Laxmi

There are three primary sources for natural dye: plants, animals and minerals. Natural dyes can be split into two groups: substantive and adjective. Substantive dyes or known as direct dyes, become chemically fixed to the fibre without the use of chemicals. Adjective dyes are referred to as the mordant dyes and need to have substance(s) added to it for the colour to stay. Plants are an unlimited source of dye, different parts of the plant provides dye, for example: stem, roots, bark, leaves, seeds and fruit. Also, some plants may provide more than one colour depending on which part of the plant the dye is extracted. The shade of dye will vary according to the time of year the plant is used, for instance, the plant’s ripeness, soil conditions, etc. Plus, during the dying process, the water used can affect the colour (if there are minerals present). (Duke and Edlin-White year unknown).
Natural sources of dye have been used for thousands of years and are still used.
There are advantages to using natural sources of dye, for example, the 5 dyestuffs can provide most colours except electric blue or fluorescent colours. From one dye, it is possible to obtain 5-15 varying colours and shades. The sources are renewable and available anywhere and anytime. There are basically no chemicals used during the dying process, which means that the dye will be organic. Another advantage is that most of the dyes used are antioxidants and free of azo compounds, which are carcinogenetic.
However, a disadvantage is that during the dying process there is a lot of water usage. The dye material will be placed in a pot of water and heated, so for the people trying to be ecological and using natural sources for dying this may not always be the case. Moreover, there may be a large quantity of the natural source needed in order to get the correct resulting colour. Eber Lopes Ferreira mentions in his book that one of the biggest problems when dying with natural sources is the fixation of the colour, even with the mordant it is harder to get the colour to stay. Another disadvantage of using natural dyes is that if the steps of the process are not followed properly and toxic chemicals come into contact with the skin, then the person is in risk of allergic reactions.
References:
Edlin-White, R. Duke, D. (year unknown) A Calendar of Common Dye Plants. England: Woolgatherings
Stephenson, L. (2008) Colour Me Natural. Available at: http://www.ecofashionworld.com/EcoFashion-Pulse/Color-Me-Natural.html (accessed at 14/02/13)
Vankar, P. (2000) Chemistry of Natural Dyes. Available at: http://www.ias.ac.in/resonance/Oct2000/pdf/Oct2000p73-80.pdf (accessed at 14/02/13)
http://www.dsir.gov.in/reports/tmreps/vegdye.pdf (no date) (accessed at: 14/02/13)
Anderson, K. (2009) Natural Dyes available at: http://www.techexchange.com/library/Natural%20Dyes.pdf (accessed at: 14/02/13)

Flint – Laxmi

97 million years ago, chalk formed at the South Downs. The chalk that was formed contained flint (SiO2, silicon dioxide) and it is the only hard rock found on the Downs, it ranks 7 out of 10 on the hardness scale where diamonds are 10. It is nearly pure silica, less than 5% impurity (calcium carbonate). The average chemical composition of flint is 94.0% SiO2, 4.9% CaO=CaCO3, 0.9% MgO and O.1% Fe2O3.
Life under the sea that had skeletons built from silica were buried and the silica was dissolved in the sea water. This was later precipitated onto the chalk sea bed. They can be found as thin layers and nodules, it is insoluble and so when the chalk has been washed away or weathered then the flint will remain.
Flint can be used to make tools mainly because it can be shaped well and as it is a hard rock it is a good tool. The process of making the shapes from flint is called flint knapping. To knap means to break into small parts or pieces with a sharp cracking sound. During this process, flint is chipped until it is the desired shape. The tool used is called a ‘lithic’. The reason flint can be shaped easily is because it has a very fine crystalline grain, which means that when it has been hit by a tool it can be chipped. A modern use of flint is a strike-a-light, by striking it against other surfaces it can cause sparks. This works because the hard flint edge will shave off particle of metal which is heated through the friction and will burn with the oxygen.
In the picture a flint has been shaped into an arrowhead and can be used to cook food or make fire, etc.

References:
South Downs National Park Authority (2011) Geology Through Time. Available at: http://www.southdowns.gov.uk/learning/themes-to-study/landscape/geology/geology-through-time (accessed at: 21/02/13)
Museum of Stone Age (2013) What is Flint? Available at: http://www.stoneagetools.co.uk/what-is-flint.htm (accessed at: 21/02/13)
http://www.flintknappingtools.com/knapping.html (accessed at: 21/02/13)
Kogel, J. Trivedi, N. Barker, J. (2006) Industrial Minerals & Rocks: Commodities, Markets and Uses. 7th edn. USA: SME (Society for Mining, Metallurgy, and Exploration, Inc.
unknown photographer (2010) Flint Knapping [online]. Available at: http://rockhoundblog.com/regular-postings/what-is-flintknapping/ (accessed at: 21/02/13)

Structure of a bud – Laxmi

The structure of a bud is a condensed shoot and it has a very short stem. The bud consists of undeveloped and dormant parts of the plant which contains the cells for rapid cell division when the conditions are right.

Inside the bud the structure of the new shoot is ready for rapid growth. The leaves are tightly packed and they overlap each other. Due to the large surface area being reduced to fit into a small space, the inner leaves will fold and crease in order to fit.

The outer leaves will be a brown or black colour and are thicker and stronger than the inner leaves. The reason for this is because the outermost leaves will protect the bud from the weather, birds, insects, fungi etc. These are the scales of the bud. At the end of the short stem you can find a flower or rapid cell division will take place where the new bud will form.

In spring the stem of the bud begin to elongate and the scales are pushed apart and the leaves will space out and unfold as the stem grows in length. Simultaneously, the scales will curl back and weeks later they will fall off. This will help the photosynthesis of the inner leaves.

Buds that are found at the tip of a stem are called terminal buds, buds found in the axil of a leaf are called the auxiliary bud and final the adventitious buds are buds that grow elsewhere e.g. on trunks or roots. The terminal buds release the hormone, auxin, for plant growth, also, forcing the growth upwards instead of outward.

References:

Mackean, D. (2013) Introduction to Buds and Twigs. Available at: http://www.biology-resources.com/plants-buds-01.html (accessed at: 21/02/13)

http://science.jrank.org/pages/1063/Buds-Budding-Plant-buds.html (no date) (accessed at: 21/02/13)

Lichens – Laxmi

What are lichens?

Single lichen consists of two or more partners living together symbiotically, one of these are fungus and the other is alga or cyanbacterium. The way that this works is the algae or cyanbacterium will photosynthesise and produce the essential nutrients that will feed both of the partners. The job of the fungus is to create a body (thallus) for both partners to live in. There are around 30,000 species of lichens around the world; they range widely in colour, shape and sizes. They can be invisible to the naked eye and can grow just about everywhere. Around the world they cover 8% of land, including some of the most extreme environments e.g. mountains, rainforests, etc.

Why lichens are useful?

Lichens can be used an indicator for the environment, lichen is very sensitive to air pollution. Where there is more pollution there will be less variety lichen. For instance, when coal burning was a major part of the industry, the sulphur dioxide killed lichen, but since the sulphur dioxide has decreased the lichen has been re-colonising the areas. There is however nitrogen compounds from road traffic and intensive farming. There are some species of lichen that thrive on nitrogen, but this can help to show where there is more nitrogen in the air.

Also, lichens can live alongside other plants/animals. It can recycle the nutrients used by other plants and provide homes for spider and other insects even mice! We can extract an amazing range of wool dyes from lichen and drug companies can use lichen for antibiotics or sunscreen cream. The fungus can produce chemicals compounds that act as sunscreen to protect the photosynthetic partner.

Lichens and logs?

Logs start to rot after a while and lichen will help to decay the log. Specie of lichens called British Soldiers (picture) help to break the wood, and puts the nutrients back into the soil, which can be reused by other plants. Lichen will grow on logs, as it perfect to get sunlight without leaves blocking the surroundings (competition). Moisture is important for maximum photosynthesis to take place as well.

References:

Loeffler, K. (date unknown) Claonia Cristatella [online] available at: http://www.fcps.edu/islandcreekes/ecology/british_soldiers.htm (accessed at: 21/02/13)

Natural History Museum (2013) Lichens. Available at: http://www.nhm.ac.uk/nature-online/life/plants-fungi/lichens/index.html (accessed: 21/02/13)

http://www.fcps.edu/islandcreekes/ecology/british_soldiers.htm (no date) (accessed at: 21/02/13)

Ontario, Ministry of Natural Resources (2013) The Sensitivity of Lichens to Forest Herbicides + Facts About Lichens. Available at: http://www.mnr.gov.on.ca/en/Business/OFRI/2ColumnSubPage/STDPROD_095257.html (accessed at: 21/02/13)

Why does an egg white turn white when it is cooked? – katie

When cooked, the white of an egg turns from a clear gel to a solid white substance. The white of the egg is also known as albumen. It contains a solution of proteins surrounded by water. In fact around 90% of the solution is water and around 10% is protein.

The proteins in the egg are made up of long chain amino acids. The bonds between these amino acids are strong covalent bonds. The proteins are also globular, which means that the protein molecule is twisted so that the protein is in a spherical shape. Weak bonds keep these molecules in the correct 3 dimensional shape.

When heat is applied it makes the molecules vibrate. The strong covalent bonds can withstand this, but the weak bonds which are usually Hydrogen bonds break which means that the 3-Dimensional protein structures unravel.

When two of these unravelled protein structures meet, they then form new bonds, which rather than binding the protein into another 3-dimensional structure bind the proteins to each other. The egg turns solid when several protein structures have joined together, forming a net. The egg turns solid because the water from the egg is now captured in this net. The egg turns white because this net of proteins means that light can no longer penetrate it. This process is also known as denaturation.

http://www.ochef.com/1231.htm

http://voices.yahoo.com/the-kitchen-chemist-happens-fry-egg-2969005.html

http://www.sumanasinc.com/webcontent/animations/content/proteinstructure.html

http://www.exploratorium.edu/cooking/eggs/eggscience.html