Three into Four Will Go

Most plants use an enzyme called rubisco to convert carbon dioxide (CO₂) into sugars containing three carbon atoms—a process known as C3 photosynthesis. But at temperatures above 25°C, rubisco begins to bond with oxygen instead of CO₂, reducing the efficiency of the reaction. As a result, certain plants in warm climates have evolved a different mechanism, called C4 photosynthesis, in which other enzymes help to concentrate CO₂ around the rubisco, and the initial result is a four-carbon sugar. In hot, sunny climes, these C4 plants are half as efficient again as their C3 counterparts. They also use less water and nitrogen. The result, in the case of staple crops, is higher yields in tougher conditions: a hectare of rice, a C3 plant, produces a harvest of no more than eight tonnes, whereas maize, a C4 plant, yields as much as 12 tonnes.

Turning a C3 plant into a C4 one, though, is trickier than conferring flood resistance, since it involves wholesale changes in anatomy. C4 plants often absorb CO₂ from the air in one type of cell and then convert it to sugars through photosynthesis in another. C3 plants, by contrast, do both jobs in the same place.

John Sheehy, one of IRRI's crop scientists, plans to screen the institute's collection of 6,000 varieties of wild rice to see if any of them display a predisposition for C4 photosynthesis. Other researchers, meanwhile, are trying to isolate the genes responsible for C4 plants' unusual anatomy and biochemistry. A few years ago, geneticists managed to get rice to produce one of the enzymes needed for C4 photosynthesis by transplanting the relevant gene from maize.

The task, admits Robert Zeigler, IRRI's director, is daunting, and will take ten years or more. But the potential is enormous. Success would not only increase yields, but also reduce the need for water and fertilisers, since C4 plants make more efficient use of both. Other important C3 crops, such as wheat, sweet potatoes and cassava, could also benefit. If it all works, a second green revolution beckons.

Source: The Economist, 2006, December 7

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2.2.1. Comprehension Questions

1. What are the reasons that urged scientists to use modern genetic techniques to improve rise yields?

2. What is the most ambitious project as far as rice is concerned? What does it consist in?

3. Why is it considered to improve yields?

4. How long will it take to work out this project?

5. What are the crops or produce that most often become the aim of such genetic technologies? Could you think of any others?

2.2.2. Key Vocabulary

ENTRY	TRANSLATION	EXAMPLES AND NOTES
paddy fields	рисовые поля	There are lots of paddy fields in China and Thailand
projection n	проектирование; план, проект	a projection of economic growth for all member states – прогноз показателей экономического роста для всех стран-членов
convert v	превращать, переделывать обращать (на путь истины, в другую веру)	convert sth into sth – превращать что-либо во что-л They converted the old school into luxury flats
urban sprawl	рост городов за счет сельской местности	Urban sprawl is consuming growing quantities of countryside
strain n	натяжение, растяжение; напряжение; тех деформация	a strain on sth – давление на что-то the strain of sth – давление чего-то under strain – под давлением, в стрессовой ситуации, в напряжении
yield n	урожай, сбор плодов; размеры выработки, выход	a yield of over 12% on overseas investments – доход около 12% по иностранным инвестициям (доходность иностранных инвестиций в 12%)
immersion n	погружение, осадка	Language immersion is a method of teaching a foreign language in which teachers and students use only the foreign language during classes
enzyme n	энзим, фермент	Enzyme is a natural chemical produced by animal and plan cells that causes reactions and other processes to start
screen v	прикрывать, защищать; просеивать, сортировать; демонстрировать на экране	screen sth from sth – защищать, прятать что-то от чего-то screen sb for sth – исследовать на наличие чего-либо
predisposition n	предрасположе-ние, склонность	an inherited predisposition towards schizophrenia – наследственная предрасположенность к шизофрении
relevant adj	уместный, относящийся к делу	relevant to – относящийся к How is this relevant to this discussion?
daunt v	укрощать; устрашать, запугивать; обескураживать	I admit I’m daunted by the job, but I’m going to try my best
embrace v	обнимать(ся); воспользоваться (случаем, предложением); принимать (веру, теорию); включать в себя	Most countries have enthusiastically embraced the concept of high-speed railways
turn one’s noses up at sth	отказаться принять что-то	Western consumers turn their noses up at genetic engineering

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