Passage 2 Findings on How Plants Breathe May Save Water
植物如何呼吸？ 《纽约时报》

[00:01]New information on how plants breathe may help scientists
[00:07]engineer plants that require less water,
[00:11]according to a report published this month in Nature Cell Biology.
[00:18]While it has been known for half a century that a plant's pores, called stoma,
[00:25]can open at varying rates depending on the concentration of carbon dioxide in the air,
[00:34]scientists did not understand how the process worked until now, said Julian Schroeder,
[00:43]a professor of biology at the University of California, San Diego. Dr. Schroeder
[00:51]and his colleagues report that they identified the specific sensors in plants
[00:59]that detect carbon dioxide and prompt a plant's pores to open and breathe.
[01:07]The tighter a plant can keep its pores, the less water it loses
[01:14]and the less water it requires to grow. And since carbon dioxide levels
[01:21]are 40 percent greater than in preindustrial times,
[01:26]it would seem that plants could now get plenty of carbon dioxide
[01:33]without losing too much water - an odd and perhaps beneficial consequence
[01:39]of the accumulation of greenhouse gases.
[01:44]The water saving strategy does not work for all plants,
[01:49]and the problem is how well they detect carbon dioxide.
[01:55]Plants with sensitive sensors can save water.
[01:59]But other plants with weaker carbon dioxide receptors are not able to
[02:05]detect the increased levels as well
[02:09]and miss the opportunity to conserve water, Dr. Schroeder said.
[02:14]His laboratory found that by adding extra copies of the receptor proteins,
[02:22]pores tightened, water efficiency increased and the plants still got enough carbon dioxide.
[02:30]Dr. Schroeder said genetically manipulating certain plants
[02:35]could provide farmers with more efficient crops.
[02:40]Wolf Frommer, a Stanford biologist who was not involved in the study,
[02:47]said that while humans found ways to battle growing carbon dioxide emissions
[02:54]and manage a diminishing water supply, the study offered one way
[03:00]to help plants cope with environmental changes.
[03:05]There is one problem, though, with helping plants conserve water.
[03:11]When plants release moisture through their pores, it cools their leaves,
[03:17]in the same way sweating cools humans. This prevents them from drying out,
[03:25]particularly in desert regions. But Dr. Frommer explained that bioengineering
[03:32]was a slow tweaking process. He said there might be another yet undiscovered gene
[03:39]that when manipulated could prompt a plant to open pores when its leaves were dry.