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Campus Currents May 2007: Volume 4, Number 2

Breathe Plant, Breathe!

Plants breathe through pores in their leaves; they also lose almost 95 percent of the water they take in through the same pores.  With atmospheric carbon dioxide much higher now than in pre-industrial times and rising, it would help many plants adapt to changing conditions if they could narrow their pores to conserve water and still get enough CO2 for photosynthesis.

UCSD biology professor Julian Schroeder’s research group has identified plant proteins that might help. Their research, reported in Nature Cell Biology, located the proteins—enzymes that react with CO2—in cells that form the openings of the pores. When they inserted extra copies of the gene for the enzyme in Arabidopsis, a plant commonly used for genetic analysis, water ­efficiency improved and photosynthesis continued normally, suggesting that altering CO2 sensitivity wouldn’t stunt growth. This is good news if the goal is to engineer drought-resistant crops with robust yields. Plants that had their genes for the enzymes disabled failed to respond to increased CO2 concentrations in the air, losing out on the opportunity to conserve water.

Crops engineered with extra copies or improved versions of the gene could be a boon in places like California where 79 percent of water diverted from streams and rivers, or pumped from the ground, goes to agriculture. However, the researchers also point out that saving water and surviving heat involves a tradeoff for plants. Evaporation of water through the pores also cools the plant, just like sweat cools human beings. If ­future growing conditions are both drier and hotter, as predicted for some parts of the world, they warn that modifications of the CO2 response will need to be carefully calibrated.

—Susan Brown