London (30.11.07)
– The world is warming, they tell us, and we must be prepared.
Many people have doubts about whether we can do enough, or even whether we
know what we are doing, so in addition to trying to stop the climate changing
we had better be ready to live with the changes should we fail.
The problems for agriculture are likely to include heat and drought. It may
not matter too much (to the British) if champagne production has to move north
from France to England as the climate warms up, but if none of the present
temperate countries can grow their staple cereals or vegetables or fruits
on which we all depend, and the tropical countries are not able to grow anything
much at all, the problems become obvious. A major goal of plant breeding is
thus to develop drought- and heat-resistant strains of our food and fibre
crops to cope with such adverse conditions.
Researchers at the University of California in Davis have generated genetically-engineered
crops able to survive droughts and to grow with only a third the amount of
irrigation water they get at present. That means that such plants could survive
periodic droughts as well as reduced irrigation on a continuing basis.
In dry regions, annual plants avoid seasonal drought conditions by having
relatively short life cycles and growing quickly during the wet season. They
maximise their chances of survival by reducing water loss through their leaves
to a minimum, increasing root growth as they reduce leaf growth, and dropping
their older leaves.
The workers at Davis looked at improving tolerance to drought by delaying
the shedding of leaves which in turn is triggered by water shortage. Using
tobacco as the model plant, they inserted a gene to interrupt the biochemical
chain of events resulting in leaf fall during drought.
Both GM and unchanged tobacco plants were cultivated under the same optimal
conditions for 40 days after which water was withheld for 15 days, so simulating
extreme drought conditions.
During the dry period, the non-modified plants in the control group wilted,
lost their green pigment and deteriorated but the GM plants remained green
and displayed no signs of severe deterioration.
At the end of the 15 days, all the plants were re-watered for one week. Those
in the control group died but their GM relatives recovered and resumed normal
growth with little reduction in seed yield.
"Surprisingly, although the genetically modified tobacco plants went
more than two weeks without being watered, they maintained relatively high
water content and continued their photosynthetic activity throughout the dry
period," said researcher Rosa Rivera.
Source:
New drought-tolerant plants offer hope for warming world. UC Davis
News and Information (26.11.07) (http://www.news.ucdavis.edu/search/news_detail.lasso?id=8439)
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