Thursday, May 17, 2018

Autumn Grapevine Colour

During spring and summer the leaves are the engine room of the vine as it is where most of the food necessary for growth is manufactured. This process takes place in the numerous leaf cells containing chlorophyll.
It is chlorophyll which gives the leaves their green colour. This chemical absorbs energy from sunlight which it uses to transform carbon dioxide and water into carbohydrates like sugars and starch.

Along with this green pigment are also yellow to orange pigments, carotenes and xanthophyll, which, for most of the year, are masked by the greater amounts of green.
In autumn, due to changes in the length of daylight and in temperature, the leaves cease the food-making process. The chlorophyll then breaks down, the green colour disappears and the yellow to orange colours become visible.
At the same time other chemical changes can occur forming additional colours through the development of red anthocyanin pigments.
Some mixtures give rise to the reddish and purplish colours while others express orange.
In other words all the different colours are due to the mixing of varying amounts of chlorophyll residue and other pigments in the leaf during the season.

At this time other changes are also taking place. At the point where the stem of the leaf is attached to the vine, a special layer of cells develops and gradually severs the tissues that support the leaf. The vine seals the cut, so that when the leaf is finally blown off by the wind or falls from its own weight it leaves behind a leaf scar.
This is called abscission. This is a fascinating and complex process. More information here.

With one or two exceptions, no Australian native plants change colour or lose their leaves in autumn so it is left to exotic plants to give us some colour other than green.
Grapevines are one of these.

Tuesday, May 01, 2018

Australian Currency

Way back in the 1960s Australia made the decision to change over from the imperial measurement system to metric (SI units)
This was done over a number of years from 1970 to 1988.
It was also decided we should first convert our currency from pounds, shillings and pence (£.s.d) to decimal.
The old system was a bit of a nightmare.
2 half pennies = 1 penny 
12 pennies = 1 shilling
20 shillings = 1 pound 
You imagine the time we wasted as school kids doing calculations based on this. 
There was some controversy when our obsessively royalist PM of the time, Robert Menzies, wanted to call the new unit of currency a Royal.
But sanity and the dollar prevailed.
The big day was 14th February 1966 and we were bombarded by various TV ads for many months before. That jingle never leaves your head!
But in the end all it meant was:
1¢ = 1d
$1 = 10 shillings.
$2 = £1
Both currencies were used in tandem for quite a while.
I was reminded of all this when I read the obituary of renowned gold and silversmith Stuart Devlin who was the designer of the original coins.
Below is a picture of the obverse side of them. The Queen's head is always on the other, even to this day.
They are (L to R) Australian coat of arms, feather tail glider, platypus, frilled neck lizard, lyre bird and echidna.
The 1¢ and 2¢ are no longer in circulation. The lowest denomination is now 5¢ and even this may be withdrawn in the not too distant future.
Paper currency started with the dollar and two dollar note progressing through 5,10, 20, 50 and 100.
The first two have been subsequently replaced by coins.
Stuart also designed the $1 coin which was released in 1984.
The $2 coin followed in1988.

Modern polymer banknotes were first developed by the Reserve Bank of Australia (RBA), Commonwealth Scientific and Industrial Research Organization (CSIRO) and The University of Melbourne. They were first issued as currency in Australia during 1988. 
In 1996 Australia switched completely to polymer banknotes.
Many other countries have also gone completely polymer including Canada and New Zealand. The latest countries to introduce polymer banknotes into general circulation include the United Kingdom and Chile.
They are more durable than paper and have the ability to incorporate many security features.
Unfortunately even this hasn't stopped the forgers, just made it more difficult.
Our $50 note is a prime target.