Acorn Galls

By Jack Scott

During our final visit to the woods last week, we made a crude ink from acorn galls. This
post will look at the process behind the formation of these galls, and the science involved
in producing the ink.

"A gall is an abnormal growth produced by a plant or other host under the influence of
another parasitic organism. It involves enlargement and/or proliferation of the host cells
and provides both shelter and food or nutrients for the invading organism."

Oak galls are formed when gall wasps lay their eggs in different parts of oak trees.
Knopper galls are produced when Andricus quercuscalicis lay their eggs in the young
catkins of oak trees. Acorn cup galls however are produced by Andricus grossulariae
laying their eggs with in the tissue of an acorn cup.

Upon hatching from the eggs, the hungry larvae begin feeding on the host tissue
surrounding them. The plant's defensive reaction to this intrusive mechanical or chemical
irritation is to isolate the toxins or activities of the invader in a tough, tumorous mass of
tissue. Ironically, in doing so the plant provides food and shelter for the developing
ravenous larvae.

Secretions from the larva, including saliva and excreta, are believed to control the
development of the gall. The gall can grow so much that the acorn and its cup are
completely hidden from view. The gall changes colour from red, to green, to brown as it
develops. After completing their growth and metamorphosis, often many months later, the
adult wasps escape by chewing a circular exit tunnel through the wall of the gall. The
precise mechanism by which different species of wasps produce such remarkably unique
galls is still being debated by cecidologists (people who study galls).

The chemical composition of galls varies depending on the gall-forming agent and the
plant in question. The acorn galls we used contain 45-50% tannic acid as well as high
concentrations of gallotannic acid. It is these acids that are needed to create ink.
Our crude attempt to produce ink involved beating acorn galls, boiling the broken pieces
with iron, and eventually straining the product through a small sieve. There are however
more precise, alternative methods which arguably produce better results. This in one such
method...


Resources
Galls, 3 parts by weight
Water, 30 parts by weight
Ferrous sulphate, 2 parts by weight
Gum arabic,1 part by weight

Method
• Break the galls into pieces, then grind them in a coffee mill.
• In a beaker, add the water to the ground galls. Leave the mixture to ferment in a sunny
corner at room temperature for 3 days.
• Filter the mixture and add the ferrous sulphate to the solution. Stir well and leave for 3
days.
• Add the gum arabic, stir the mixture and you have your ink.


After the galls have been broken up, the reactions occur in two stages: the fermentation of
gallotannic acid to gallic acid followed by the formation of the ink pigment. What follows is
an explanation of these processes. Whilst not easy to follow, it certainly gives all the
information needed...

"Galls contain large amounts of gallotannic acid but relatively little of the gallic acidneeded to make the ink pigment. In the fermentation stage, the galls release theenzyme tannase from the Aspergillus niger and Penicillium glaucum fungi that arefound in the galls. Over three days, tannase catalyses the hydrolysis of gallotannicacid to gallic acid and glucose. 

The ink pigment is formed in two further stages: a Lewis acid-base reactionfollowed by a redox reaction. 

Gallic acid and ferrous sulphate form ferrous gallate (a colourless water-solublecompound), plus H3O+ and SO42-. 

Almost immediately, the ferrous gallate reacts with oxygen to produce water andferric pyrogallate, a black insoluble octahedral complex in which the ligands ofeach ferric cation are two molecules of gallic acid. 

The ink pigment is ferric pyrogallate. Owing to the presence of H3O+ ions, thesolution is acidic."

Yikes! Hope you got all that. Essentially, the tannins present in the galls are what
eventually produce the ink. This process (or slight variations) has been used for hundreds
of years in many different countries. So, from the parasitic larvae of a gall wasp came the
the works of Shakespeare, the American Declaration of Independence, and my sketch
from our final adventure in the woods.

I'll let you decide which of these will have the greatest lasting impact on civilisation.









Sources
http://waynesword.palomar.edu/pljuly99.htm
http://www.bugsandweeds.co.uk/galls%20p1.html
http://therealknowhow.com/2012/02/28/making-oak-gall-inkdye-using-acorns/
http://www.scienceinschool.org/2007/issue6/galls
http://natureinfocus.wordpress.com/2011/11/14/acorn-knopper-gall/
http://www.wildlifetrusts.org/species/knopper-gall

Marshmallows

The science of toasting marshmallows

The science behind toasting marshmallows

When marshmallows are toasted, a chemical change occurs. The sugar molecules in the marshmallow are being changed into carbon (1). Sugar can be changed into water molecules. When you toast marshmallows, the heat causes a chemical reaction producing water molecules which then evaporate, leaving the carbon behind (4).

A marshmallow undergoes a six-step transformation before it becomes a toasted marshmallow: 

1. The swelling - as you heat the marshmallow, the moisture inside expands, which causes the marshmallow to swell (2).
2. The escape - as the moisture expands, it creates tiny holes in the marshmallow, which allow the moisture to escape as steam (2).
3. The sugar rush - as the marshmallow does not now have moisture, it is a sucrose char. Oxygen in the air rushes to the surface of the marshmallow (2). 
4. The flame on stage - oxygen diffuses to the surface of the marshmallow from the surrounding air. At the surface of the marshmallow, carbon reacts with oxygen, which produces a blue flame (2). 
5. The oxidation stage - carbon atoms combine with oxygen atoms to produce carbon monoxide, and then carbon dioxide (2)
6. The oxyinterruptus stage - as you remove the marshmallow from the fire and blow the marshmallow out, the oxidation process is interrupted, creating soot which is evidence of incomplete combustion: hydrocarbon + oxygen    →    carbon monoxide + carbon + water (2). 

How to cook the perfect marshmallow

You want to put your marshmallow slightly to the side of the flames and in an area of glowing coals. Above the fire, the heat coming up is known as the convective flow (hot gases coming off as flames). If you hold the marshmallow here, the marshmallow can catch on fire if you are not careful. If you want the perfect toasted marshmallow, you need to cook it using radiant energy (heat coming off of the glowing coals). Marshmallows are actually like pieces of fuel as they are made of sugar (carbon, hydrogen and oxygen). Therefore, it is easy to catch marshmallows alight over a fire (3). 

Making marshmallows

Marshmallows are a fun and enjoyable experience when sitting around a campfire. Toasting your marshmallows makes them brown and crispy on the outside, but soft and gooey on the inside! You can even make your own homemade marshmallows as shown in this video: http://www.youtube.com/watch?v=otb9AIGXMaM

For vegans, it is still possible to enjoy this marshmallow experience by following the recipe in this link: http://www.foodmyfriend.com/2012/07/vegetarian-marshmallows/. These marshmallows will still be gooey and soft when heated over the campfire, so vegans are no longer missing out on this tasty treat! 

By Lauren Watmough

(1) http://www.youtube.com/watch?v=mgDFxgtsCHk

(2) http://www.fitnessandfreebies.com/food/toastmarshmallows.html

(3) http://www.npr.org/player/v2/mediaPlayer.html?action=1&t=1&islist=false&id=154781777&m=154828858

(4) http://eatsleepscience.com/ess/index.php?option=com_content&view=article&id=49:marshmallow-science&catid=34:ess-details&Itemid=50

why animals hibernate

Following on from Sam’s blog entry on badgers, I began to wonder why animals hibernate, I have my theories but through reading other blog entries, I have found some of my theories to be untrue.

Animals hibernate to conserve energy over winter when food in scarce, they have the ability to reduce their body temperature to almost match the temperature outside, for days, weeks and even months at a time to conserve their energy. They also conserve their energy by not moving and also by slowing their metabolisms. The animals breathing and heart beat also slows down, all these elements combined help animals survive the cold months during winter.

Many people, me included, think that hibernation would be restful, but it is not. Some animals are so exhausted after their hibernation; they need to sleep more once they stop hibernating to recover.

Hibernation is very different to sleeping, when sleeping the animals can wake easily and move around during sleep. During hibernation animals appear lifeless and often take a long time to be woken and even longer to begin moving.

To prepare for hibernation, animals eat more food to store as fat to live on throughout their hibernation. Interestingly animals do not lose any muscle during hibernation and wake just as strong as they did before they went to sleep.

Some animals don’t hibernate straight through winter, but stores food with them and wake occasionally to eat and then goes back to hibernation.

There are two different types of hibernators:

Warm blooded

	Badgers		Hedgehogs
	Bats		Nighthawks
	Chipmunks		Poor-Wills
	Dormouse		Prairie Dogs
	Fat-tailed lemurs		Raccoon
	Ground squirrels		Skunks
	Hamsters		Swifts
	Marmots, Groundhogs, Woodchucks		And bears [depending on who you talk to]

 

And cold blooded

	Bees
	Earthworms
	Frogs and toads
	Lizards
	Mud Turtles
	Snails
	Snakes

 Amy Spencer

Bibliography

http://www.howitworksdaily.com/environment/why-do-animals-hibernate/

http://library.thinkquest.org/TQ0312800/hibernate.htm

Lichens

Lichens

Whilst visiting the forest, we came across trees and logs containing lichens. We wondered what they were and wanted to find out a little more about them. After doing some research, I found out the following:

There are around 25000 species of lichens. Lichens are named according to the species of fungus involved. Lichens are found in many parts of the world, even polar regions and high altitudes.  They can grow on rocks, wood or firm soil. They grow very slowly and most are a grey-green colour. However, they can also be white, yellow, yellow-green, red, orange, brown or black (2). Lichens are formed by a fungal partner (mycobiont) and an algal partner (phycobiont) (1). The fungi and the algae have a symbiotic relationship. It has been found that the algae makes food for the lichen through photosynthesis and the fungi provides protection for the algae and obtains water and minerals for the lichen. When algal and fungal cells combine, they form a structure known as a thallus. The thallus is the visible body of the lichen. In many lichens, the algal and fungal cells inside the thallus produce chemical compounds that neither the algae of fungi can produce independently (2). The shape of the thallus is used by scientists to classify lichens into three main types:

     · Crustose Lichens (e.g. brown crust lichen. They are crust like and can attach to rocks) (2)

     · Foliose Lichens (e.g. dog-tooth lichen. They are flat and have leaf-like structures) (2)

     · Fruticose Lichens (e.g. reindeer moss. They have erect or hanging branch-like structures) (2)

Lichens and the nitrogen cycle

Lichens contribute to the nitrogen cycle as they convert nitrogen in the air into nitrates which contribute to their growth and development. Their contribution to the nitrogen cycle is also beneficial to plants because when it rains, nitrogen leaks from living and dead lichens and is available to plant life in areas around it. When lichens die, they give decayed organic matter to the area in which they inhabited, enabling mosses and seeds from vascular plants develop in the new soil (3).

                                                Lichens turn nitrogen in the air (N2) into nitrates (NO3-)

Reproduction of lichens

Lichens can reproduce both sexually and asexually. They can develop sexually by producing spores which develop into fungi. Wind/rain transports algae to this fungi to produce a lichen (2). Lichens reproduce asexually in two ways: by producing soredia (a cluster of algal cells wrapped in fungal filaments) which then disperse to form new lichens, or by producing isidia (like soredia but they are enclosed within a layer of protective cortex tissue). Isidia break off and colonise new areas (4).

Lichen grow in many conditions

Most lichens are temperate or arctic. They tend to grow better in drier environments. Their secret of success is not fully understood, however their ability to survive drying and their complex chemistry are important aspects (4) (the chemistry of the lichen pigments is complex. It involves a diversity of oxygen ring compounds, called ‘lichen acids’) (7). Lichens can survive a complete loss of body water. When moisture becomes available again, they quickly absorb this water, becoming soft and fleshy again. Whilst they are dry and brittle, pieces may flake off, which may then later grow into new lichens (4).

How do lichens feed?

Lichens do not have roots, stems, flowers or leaves. However, the algae photosynthesise. They can photosynthesise when the temperature is well below freezing (5). The algae photosynthesise like plants, however different mechanisms are used. In algae photosynthesis, chlorophyll is not always the primary pigment. A wide variety of accessory pigments may be used in algae to photosynthesise, which is why algae are found in so many different colours (6).

Economic benefits of lichens

Lichens have been a source of natural dyes for wool and fabric for many years. To make lichen dyes, you can boil them in water for several hours. The pH may be altered by adding vinegar or washing soda to get the desired colour. Lichen dye can also be produced by slow fermentation of the lichen in aqueous ammonia for a couple of weeks (7).
Some lichens have antibiotic properties. Europe uses the genus Usnea in ointments and other commercial products. It is said to aid healing in wounds (3).
Lichens have been used in deodorants, laxatives, tonics, and healing pastes. Research has begun to show that lichens may be able to be used to fight against some cancers and viral infections, such as HIV (3).

Lichens growing on trees

In the northern hemisphere, lichens tend to grow on the north side of the tree. Because direct sunlight does not hit the north side of the tree, the bark there hardly dries out, creating a good environment for lichens to grow. Lichens usually grow around the entire tree. However, there tends to be a more dense area of lichens on the north side of the tree, as there is more moisture there (8).

Why do lichens grow on logs?

Logs do not contain any leaves, therefore there is no competition for lichens to get sunlight. The log also provides the lichens with moisture. Therefore, the sunlight and moisture availability provide good conditions for the lichens to photosynthesise.

By Lauren Watmough

     (1)    http://www.ucmp.berkeley.edu/fungi/lichens/lichenlh.html 

     (2)    http://science.howstuffworks.com/life/fungi/lichen-info.htm

     (3)    http://ohioline.osu.edu/sc195/029.html

     (4)    http://www.ucmp.berkeley.edu/fungi/lichens/lichenlh.html

     (5)    http://www.mnr.gov.on.ca/en/Business/OFRI/2ColumnSubPage/STDPROD_095257.html

     (6)    http://www.iscid.org/encyclopedia/Algae_and_Bacterial_Photosynthesis

     (7)    http://www.fao.org/docrep/v8879e/v8879e07.htm

     (8)    http://www.ehow.com/info_8517996_lichen-only-one-side-tree.html

Evolution

Following our nature walk before easter i began thinking about the process of evolution. Evolution was proposed almost simultaneously by two men, Charles Darwin as we all know, and Alfred Wallace (1). Evolution is driven by the struggle of living things to survive long enough to reproduce.Darwin and Wallace both noticed that animals often have many more offspring than are able to survive.

Geese have many goslings, a large number will not survive.

 They also saw that traits present in the parents were also present in the offspring. Now this was before the discovery of DNA so Darwin and Wallace did not know what caused this, but they knew it must be important. Today we know that these changes within a population are caused by a slight mutation of the genetic code, if this mutated genotype leads to a helpful phenotype then it may be passed on to future generations.

This is where the process known as 'Natural Selection' begins. Some animals inherited traits that gave them a higher likelyhood of surviving to reproduce. These animals will then pass successful traits to their offspring. Over time these traits may become more and more pronounced. (2) Now these changes can be anything from a different shaped beak that allows them to feed on something that their competetors can't, to a slightly different hip shape that allows an ancient primate to stand on its back legs for longer (2), you can see where the term 'survival of the fittest' come from.

The varied beaks of these finches allow them to avoid competition by feeding on different things.

 After many generations have passed, these differences will build up until the decendents of the original mutation will appear radicaly different (4). This will eventualy lead to the creation of a new species. After  Evolution is not limited to animals, though its effects may be more obvious, exactly the same processes happen in plants, bacteria and fungi, traits that allow for succesful competition will always florish in a population.

Not all changes however are based on survival to breed, others are know as 'Sexual Selection' (3). In this situation, traits that are desirable are chosen, usually by the female, are selcted for. In Birds of Paradise, males are often brightly coloured and put on complex dispays in order to attract a much less colourful mate.

The male dances to attract a mate, a bit like clubbing really.

A successful male will pass on his genes to his offspring, passing on traits that increase their chances of mating themselves.

The evidence for evolution is overwelming, fossil evidence combined with observations of nature show us that organisms change over time and produce the wonderous variety that we see everyday.

By
Rob Jones



(1) http://www.nhm.ac.uk/nature-online/evolution/what-is-evolution/the-theory/index.html
(2) http://www.nhm.ac.uk/nature-online/evolution/what-is-evolution/how-does-evol-work/index.html
(3) http://www.nhm.ac.uk/nature-online/evolution/sexual-reproduction/index.html
(4) http://www.newscientist.com/article/dn9953-instant-expert-evolution.html

Redwoods

How are Redwoods fireproof?

During a walk in the forest, we came across a Redwood. Having been told that Redwoods are actually resistant to fire, I wanted to find out more ... 

A bit about redwoods

Redwoods originate from California. Redwoods are known for their longevity, living for 500-1000 years, and sometimes 2000 years or more. They flower during the later autumn/early winter and produce male and female flowers on the same tree. The male flowers produce pollen and appear as small yellow/brown tufts at the end of leaves throughout the tree. The female flowers are embryonic cones. They appear green and only at the ends of the branches of the upper part of the tree. (3) There are actually three types of Redwood: the Giant Redwood (Wellingtonia), the Coast Redwood (Sequoia sempervirens) and the Dawn Redwood (Metasequoia glyptostroboides). The Giant and Coast Redwoods both have properties that make their bark fire resistant (1).
The Giant Redwood: This type of Redwood is the biggest of them all. Giant Redwoods thrive in a moist, humid climate. (2) They are recognised as being the heaviest of all trees. It can live for over 3 thousand years, reaching a height of more than 100 metres. The bark is soft and spongy. It is also very thick, being up to 2 feet thick in mature trees. The trunk has a conical outwards sweep. The Giant Redwood has short, spiky leaves. Its seedlings need the right conditions to grow and develop quite slowly in the first six months (1).

                                               

                       

                   (9)                                                                                                 (1)                                                                                               

                                                                                              

The Coast Redwood: This Redwood is recognised as the tallest tree. Their native habitat is California, where they grow to around 110 metres. The bark is thick and relatively soft. Its trunk has a more parallel profile at the base. The leaves are flat, soft and shaped (1).

 

                                                                                 (1)


             (10)                                                                             

The Dawn Redwood: This Redwood had been thought to have been extinct for many years until living examples were located in China. They are now spread across the globe. They are rare but can be found in many parts of the world. The Dawn Redwood is a conifer, however, it is deciduous. The branches grow in an upwards direction. It has fine, flattened, delicate looking leaves. Before falling in the autumn, the leaves become a bright orange. The trunk is quite slender and the overall profile is relatively straight. It grows where there is plenty of water, and in moderately swampy conditions (1).

 

(11)


                                                                                       (1)

So, how are Redwoods fireproof?

It is only the Giant and Coast redwoods that are fireproof. These Redwoods are fireproof as they have thick bark, containing tannin, which protects them against fire (along with insects, fungus and diseases). There is also a lot of water contained in the wood itself (a large Redwood tree holds around 34000 pounds of water, transpiring about 200-500 gallons of this a day). Furthermore, the tree does not contain ‘pitch’, which is very flammable (4). Mature Redwoods are more resistant to fires than young Redwoods due to the fact that mature Redwoods have a thicker bark. Because the tree has thick bark, fire will not burn through this bark easily. Even if the fire does burn through some of this bark, the part of the tree that keeps it alive is beneath this (the phloem, cambium, sapwood and heartwood), therefore, the thick bark helps protect the tree against fire (5). Obviously, water puts out fires, so the fact that Redwood trees contain a lot of water is advantageous in the fire resistance aspect of the tree. Pitch is a highly flammable hydrocarbon concealed by softwood conifers. Native Americans valued pitch as a means of starting fires. They used kindling containing pitch to help them start fires (6). As these Redwood trees do not contain pitch, it reduces the flammability of the trees compared to other trees containing pitch.

Fire can still, however, kill Redwood trees

Despite Redwoods being fire resistant, repeated fires might reach the heartwood through cracks in the bark. The damaged heartwood will decay, causing the tree to be ‘hollowed out’. However, the outside layers remain intact and still grow. These trees can also be killed as the fire damages the bark. Fungi can then invade the damaged wood and cause it to rot (4).

                                           
(4)                                                                                             (4)
                                                                                                                

Redwoods are also resistant to insects and fungi

The Coast Redwood is occasionally infected by the larva of a small insect which reduces bark under the surface to a fine powder. However, this does not endanger the life of the tree (7). The tannin in the bark also provides protection against insects and fungi.  Tannins act as a defence mechanism against pathogens. When consumed, they induce a negative response which may be instantaneous. The two main categories of tannins that impact an animal’s nutrition are hydrolyzable tannins (Hts) and condensed tannins (proanthocyanidins) (8). Many trees are affected by fungi which then cause them to die after being damaged by a fire. However, as these Redwood trees are fire resistant, fungi do not tend to grow on the trees, meaning Redwoods are almost never killed by fungi (7).

By Lauren Watmough

     (1)    http://www.redwoodworld.co.uk/redwood_types.htm

     (2)    http://www.visitsequoia.com/redwoods-and-sequoias.aspx

     (3)    http://www.flowersociety.org/Redwood-profile.htm

     (4)    http://www.shannontech.com/ParkVision/Redwood/Redwood2.html

     (5)  http://dwb.unl.edu/teacher/nsf/C10/C10Links/ericir.syr.edu/Projects/Newton/12/Lessons/redwoods.html

     (6)    http://www.ehow.com/info_12000889_pitch-safe-fireplaces.html

     (7)    http://www.nps.gov/history/history/online_books/shirley/sec6.htm   

     (8)    http://www.ansci.cornell.edu/plants/toxicagents/tannin.html

     (9)    http://mitchgreenesbizadvice.wordpress.com/2011/05/19/these-lice-are-public-thats-crazy/   

     (10) http://en.wikipedia.org/wiki/Sequoia_sempervirens

     (11) http://www.mediahex.com/Dawn_Redwood