Book 2 Listening (1108796), страница 13
Текст из файла (страница 13)
They are, rather, deliberatelyinduced, usually by exposing seeds to radiation. And that is exactly what Tomoko Abe andher colleagues at the Riken Nishina Centre for Accelerator-Based Science in Saitama,outside Tokyo, are doing with rice. The difference is that Dr Abe is not using namby-pamby xrays and gamma rays to mutate her crop, as is the way in most other countries. Instead sheis sticking them in a particle accelerator and bombarding them with heavy ions - large atomsthat have been stripped down to their nuclei by the removal of their electrons.
This producesbetween ten and 100 times as many mutations as the traditional method, and thus increasesthe chances of blundering across some useful ones.Dr Abe's plan is to use these mutations to create salt-tolerant rice. She has tried to dothat several times in the past, but the result did not taste very nice. Her latest effort wasstimulated by the flooding with seawater of almost 24,000 hectares of farmland by thetsunami which followed an earthquake in March last year. Salt-tolerant rice would, though, beof much wider use than just restoring the paddies of Miyagi prefecture and its neighbours, theworst affected part of the country, to full productivity.
About a third of the world's rice paddieshave salt problems, and yields in such briny fields may be half what they would be if thewater in them were fresh.To induce the mutations, Dr Abe bombarded germinating seeds with carbon ions for 30seconds. She then planted them in fields in Miyagi.
Of 600 seeds that have undergone thistreatment, 250 thrived and themselves produced healthy seeds.The next stage of the project, to be carried out this month, is to take 50 grains fromeach of the successful plants and repeat the process with them. The resulting specimens willthen be sorted and the best (i.e., those that have flourished in the saline soils of Miyagi'spaddies) selected for crossbreeding, in order to concentrate desirable mutations intoreproducible lines of plants.
The result, Dr Abe hopes, will be a viable salt-tolerant strain thatis ready for market within four years. With luck, this time, it will be a tasty one as well. (FromThe Economist, May 5, 2012)Script 19. Decaffeinating wasteBrewing a solutionGenetic engineering may clean up the processing of coffeeCoffee is big business. One consequence is a lot of caffeine-rich waste which cannot bethrown away willy-nilly because caffeine is a pollutant. It inhibits both the germination ofseedlings and the growth of adult plants, so it must be collected and dumped at approvedsites.This is a pity for two reasons. One is that it increases the cost of a cup of coffee.
Theother is that the waste is rich in nutrients. If it could be decaffeinated, it might be used asanimal feed - thus adding to coffee companies' revenues rather than subtracting from them.But that would require a cheap way to decaffeinate it. Which is what Jeffrey Barrick of theUniversity of Texas at Austin and his colleagues hope they have found. Their research,published in Synthetic Biology, suggests the answer lies with genetically modified bacteria.53The idea of using bacteria to decaffeinate waste is not new. Past studies showed that aspecies called Pseudomonas putida can chew the molecule up.
But it does so in smallquantities, and no one knew enough about it to work out how to increase its efficiency.Dr Barrick thought the best way round this was to take the caffeine-chewing mechanismout of P. putida and put it into Escherichia coli, a species biologists are good at manipulating.He and his colleagues therefore extracted the cluster of P.
putida's genes that encode thecaffeine-chewing enzymes and transferred them into E. coli.And not just any old E. coli. The strain they picked lacked a gene from the pathway thebug usually uses to synthesise guanine, one of the four chemical bases that act as thegenetic code in DNA. This was to test whether the transfer had worked, because thetransplanted biochemical pathway turns caffeine into xanthine, a molecule E. coli can makeinto guanine without the missing gene. Since nothing can reproduce without guanine in itsDNA, the researchers had merely to sit back and see if their engineered bugs multiplied inthe presence of caffeine.
Sadly, they didn't.An examination of the problem showed that the transferred gene cluster was missing acrucial piece. That, they fixed using a patch from a third species, Janthinobacterium. Thenthey tried again. This time the bacteria bred like bill y-o.The next step will be to see if what works in a lab also works on an industrial scale. If itdoes, then coffee companies should see their costs reduced, and other producers of wastethat requires specialised disposal will have a new line of inquiry to pursue. (From TheEconomist, Economist April 06, 2013)Script 20.
High-tech farmingThe light fantasticIndoor farming maybe taking rootA grey warehouse in an industrial park in Indiana is an unlikely place to find the future ofmarket gardening. But it is, nevertheless, home to a pristine, climate controlled room full ofeerily perfect plants.
They grow 22 hours a day, 365 days a year in 25-foot towers,untouched by pests and bathed in an alien pink light. Critical to this $2.5m techno-Eden, runby a firm called Green Sense Farms, are the thousands of blue and red light-emitting diodes(LEDs) supplied by Philips, a Dutch technology firm. The light they give off is of precisely thewavelength craved by the crops grown here, which include lettuce, kale, basil and chives.The idea of abandoning the sun’s light for the artificial sort is not new. It offers plenty ofadvantages: no need to worry about seasons or the weather, for instance, not to mention theability to grow around the clock (although a couple of hours a day are necessary, says Gusvan der Feltz of Philips, for the plant equivalent of sleep).Moving plants indoors allows them to be coddled in other ways, too.
Water can berecycled continuously, and sensors can detect which nutrients are missing and provide themin small, accurate bursts.However, LEDs offer a host of benefits over traditional, fluorescent growing lights. Forone thing, they are far more efficient, which helps to keep electricity bills down. Highefficiency means less heat, which makes air conditioning cheaper.
Being cooler, the lightscan be placed closer to the plants, so the crops can be planted more densely. Thewavelengths of the light can be fine-tuned so that lettuce is crisper, or softer, says RobertColangelo, the president of Green Sense Farms. Your correspondent tasted soft, sweet kalenibbled straight off the plant. It was delicious.The crops grow faster, too. Philips reckons that using LED lights in this sort ofcontrolled, indoor environment could cut growing cycles by up to half compared withtraditional farming.
That could help meet demand for what was once impossible: fresh, locallygrown produce, all year round.Hydroponic, naturally lit greenhouses, such as those built by Bright Farms, a firm basedin New York, are already supplying produce to cities such as Chicago and New York. GreenSense Farms is not the first to try growing under LEDs, and despite their efficiency, energycosts have been a challenge for its predecessors.
But Mr Colangelo is confident. LEDs are54becoming cheaper all the time, and the involvement of Philips, which has invested heavily inthe technology, suggests that costs can fall further.Farms such as these are unlikely to be suitable for heavy crops like corn and potatoeswhich grow pretty efficiently in vast fields. But if Green Sense Farms can prove itscommercial worth, this form of farming could become widespread for leafy greens and otherhigh-value crops.
A new national climate assessment, published on May 6th, sets out thethreats that American agriculture is facing, such as growing numbers of insects and otherpests and a rising incidence of bad weather. Indoor farming is, happily, immune to both.(From The Economist, May 17, 2014)55Unit 9. Human genetics and diversityScript 21. EvolutionThe value of a good editorA hitherto-unknown way to evolveIn 1958 Francis Crick, one of the codiscoverers of the double-helical structure of DNA,spelled out what came to be called the "central dogma" of molecular biology.
In a nutshell,this says that DNA makes RNA, which makes proteins. In other words DNA - which carriesan organism's genetic code - "writes" that code into bits of RNA, a similar, but not identicalmolecule. These then act as messengers which tell a cell's protein-making machinery what tomake.It is a pithy and memorable summary.
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