New Understanding of How Plants Use Water

This is the VOA Special English Agriculture
Report.

Scientists have
discovered more details about how plants use water. Their findings could help to
engineer plants that grow better and more effectively in conditions with higher
levels of carbon dioxide.

Plants
naturally take in carbon dioxide they need for photosynthesis, the process of
changing light energy to chemical energy. The carbon dioxide enters the plants
through tiny holes or pores on the surface of leaves.

However, each time a plant takes in one molecule of
carbon dioxide gas, it loses hundreds of water molecules.

Scientists say plants lose
ninety-five percent of the water they take in through these pores. Some plants' pores can tighten to save water during
conditions of high carbon dioxide. Other plants are not able to do this as
well. Now, scientists know how these tiny pores tighten in plants.

Julian Schroeder is a professor of biology at the
University of California, San Diego. Mister Schroeder says that carbon dioxide
levels in the atmosphere are much higher now than they were in the past.
However, he says, many plants are not closing their pores in order to hold in
more water.

He and his team
have identified proteins that control the tightening of a plant's pores. The
proteins are enzymes called carbonic anhydrases. The findings were published last month in the
journal Nature Cell Biology. Mister Schroeder believes the enzymes could be changed
in some plants to increase their ability to store water.

The
researchers added carbonic anhydrase genes to plants that do not react to
higher levels of carbon dioxide. They observed
that for every molecule of carbon dioxide taken in by the plants, they lost
forty-four percent less water.

The scientists say the photosynthesis process continued
normally in these plants. They say this suggests that changing plants to save
more water will not affect plant growth. This method might be used to help
engineer food crops that are resistant to extremely dry conditions. The
discovery could help farmers meet a growing demand for food as water supplies
decrease. However, the scientists say
more research is needed.

And
that's the VOA Special English Agriculture report, written by Brianna Blake. For
transcripts, MP3s and podcasts of our reports, visit us on the Web at voaspecialenglish.com.

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