The trouble with truffles
QUESTION As wild truffles are so expensive, why are they not cultivated like mushrooms? The life cycle of the truffle is complex, closely associated with the success of other plants and not completely understood. In scientific terms, truffles are a group of — mostly — edible mycorrhizal fungi. The most well-known truffles are subterranean fungi of the genus Tuber, class Ascomycetes.
Truffles form a symbiotic relationship with their host plant, primarily oak, but also hazelnut, beech or birch trees.
More precisely they are ectomycorrihizal fungi, i.e. they form a sheath around the root tips of their host plant. From this sheath, tongues of tissue run in between the outer layers of the root to produce a three- dimensional structure called a hartig net.
On the outside of the sheath, fungal hyphae (feathery filaments) run out into the soil. It is this structure that allows an exchange of elements between the fungus and the tree. The fungus gets carbohydrates from the tree and in return helps the tree take up water and nutrients from the soil.
The problem for cultivators is that the symbiotic relationship is only necessary in a stressed environment: if the tree is able to easily obtain mineral nutrients and water, it ceases to depend on the fungus which is quickly outcompeted by other fungi. The required conditions are difficult to maintain artificially.
One issue is its geographic distribution. The truffle is adapted to live in temperate Mediterranean environments of Southern europe where the climate typically has well- defined seasons (hot summers and cold winters), with precise patterns of rainfall.
They also require calcareous soil conditions that have high ph and calcium levels. In europe these conditions are best found in Southern France, but there are similar areas in the UK, such as the Chilterns and North and South Downs, as well as hampshire, Wiltshire and westwards into Dorset, and the area between hull and Lincoln.
Another problem for the truffle is distribution. They require animals (usually porcine) to detect and consume them, and so disperse their spores.
To that end, the reproductive strategy of truffles has led this fungus to be able to emit volatile compounds (aroma) to attract their natural distributors. This is why they produce such a strong odour and taste and why pigs and boars are used to locate them.
Truffle cultivation is possible and was once a thriving industry. In the early 19th century, the French farmer Joseph Talon (1793-1873) became the first to recognise the relationship between truffles and oak trees, famously advising family and friends: ‘If you want truffles, plant acorns.’
By the end of the 19th century, truffles were successfully cultivated. Following the grape phylloxera crisis at the end of that century, grape vineyards were replanted with oak trees and the golden age of truffle production began.
At the beginning of the 20th century, truffle production in France reached 1,000 tons. But after World War II farming policy saw a move away from traditional smallholdings and the rise of agribusiness and large cereal farms reliant on fertilisers and pesticides, this proved ruinous to truffle growth.
So poor is our understanding of the complexity of the growth patterns that despite attempts at commercial production in New Zealand, Australia, Chile and the U. S., global yield has dropped to about 100 tons per year.
Giles Forrester, Amersham, Bucks.
QUESTION Why is the instrument panel on a car called the dashboard? ABOUT 35 years ago, the company I worked for was asked to manufacture a replica of a Bradford horse-drawn tram. The only information available was just one black-and-white photograph circa 1850.
We contacted the National Tramway Museum at Crich for assistance and were allowed to compare all different tram designs of the era. On one drawing the vertical plate in front of the driver was called the ‘ dash plate’. Checking the dictionary, ‘dash’ was defined as the ‘dirt thrown up by horses’ hooves’.
As horse-drawn transport was the main mode of road transport, prior to the advent of the automobile, the roads were covered with horse droppings and the plate was more akin to the modern mudguard.
So it is a fair assumption that when the early cars arrived on equally dirty roads, the dash plate was copied, and as instruments were added, it was the obvious place to mount them. hence the dashboard.
R. C. Hudson, Doncaster.
QUESTION Does the Earth’s total weight, including everything in it and on it, remain constant, or does it fluctuate? WheN people build structures on earth, it doesn’t add any mass to the planet since they are using matter that’s already here. It just changes shape. Most satellites and rockets that end up in orbit will eventually fall to earth.
however, there is a significant net annual loss of mass from earth each year. Although it accumulates 40,000 to 50,000 tons of mass annually from space dust and debris, it loses significantly more, about 16 tons through energy loss from the earth’s core.
The biggest mass loss comes from escaped hydrogen, about 95,000 tons, and to a lesser extent, helium, about 1,600 tons. These elements are too light to stay permanently within earth’s gravity well, so they tend to escape into space.
The net loss is about 50,000 tons or 0.000000000000001 per cent of the earth’s total mass (5,972,000,000,000,000,000,000 tons) every year.
Ed Green, Birmingham.
QUESTION Are there any films in which chess is the central theme? I’m trying to get my children interested in the game. FUrTher to the earlier answer, The Thomas Crown Affair (1968) features a famous chess scene, the game perfectly expressing the sexual tension between the characters played by Steve McQueen and Faye Dunaway. Perhaps not the most educational, but a great piece of film making.
A 1992 thriller, Knight Moves, involves a series of murders related to chess moves made during a tournament on a secluded island. It stars Christopher Lambert and Diane Lane and is pretty good.
Mrs Deirdre Marsh, Exeter.
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