( An important source of uncertainty in p...)UCSD study reveals how plants respond to elevated carbon dioxide

The study, published in the May 1 early on-line edition of the journal Proceedings of the National Academy of Sciences, shows how the level of carbon dioxide in the atmosphere controls the opening and closing of leaf stomata--pores through which plants "breathe" in carbon dioxide.

The researchers say that their findings provide important insights into the cellular and genetic mechanisms through which increasing carbon dioxide emissions will impact the world's vegetation. The study will be published May 9 in the print edition of PNAS.

"As human activity continues to raise atmospheric carbon dioxide levels, a better understanding of how plants respond to carbon dioxide is becoming imperative," said Julian Schroeder, a professor of biology at UCSD who directed the project. "Our results provide new insights into how an increased concentration of atmospheric carbon dioxide leads to changes within a plant cell that trigger the closing of the stomata--the breathing or gas exchange pores in the leaf surface."

One of the standard arguments against taking action to reduce emissions of carbon dioxide from the burning of fossil fuels is that the elevated carbon dioxide will stimulate plants to grow faster. The assumption is that plants will take up excess carbon dioxide to produce carbohydrates--their stored energy source.

However, studies have shown that, contrary to expectations, increased carbon dioxide does not accelerate plant growth. Previous research has also shown that the doubling of atmospheric carbon dioxide expected to occur this century can cause leaf stomata to close by 20 to 40 percent in diverse plant species
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Source:University of California - San Diego