A Carbon-Storage Theory Iced
A recent series of experiments in the Alaska tundra have debunked the theory that as temperatures rise, tundra ecosystems will flourish and store carbon underground, slowing the pace of global warming.
Five researchers from the University of Florida at Gainesville, the University of Alaska at Fairbanks and the Marine Biological Laboratory in Woods Hole, Mass., have found that over the course of 20 years, deliberate fertilization led to a net loss of about 25 percent of the carbon in the tundra soil, or 4.4 pounds carbon for every 10.8 square feet.
The researchers -- led by Michelle C. Mack from the University of Florida's botany department -- published their results in the journal Nature. They warned that high-latitude warming could accelerate carbon loss from soil, "causing a net loss of ecosystem carbon and a positive feedback to global warming."
Wendy M. Loya, an ecologist at Michigan Technological University who wrote an accompanying article, said in an interview that carbon stored in the soil of northern Arctic and sub-Arctic ecosystems "equals two-thirds of the amount presently found in the atmosphere." Given that these areas are most vulnerable to warming, she said, if they start releasing large amounts of carbon into the air in future decades, "it's a huge deal."
-- Juliet Eilperin
Emotions, Heart Disease Linked
Scientists have found a new link between emotions and disease -- people who are angry, hostile and depressed have higher levels of a protein in their blood that has been associated with heart disease.
Edward Suarez of Duke University and colleagues asked 121 healthy men and women to take personality tests that assessed their levels of anger, hostility and depression, and then tested their blood for a substance called C-reactive protein (CRP).
A growing body of evidence has suggested that people who have high levels of CRP are more prone to heart attacks and stroke. CRP is produced by the liver in response to inflammation in the body. Higher levels of inflammation are thought to increase the risk for a variety of health problems, including heart disease.
The study subjects who scored high on the tests for anger, hostility and depression had CRP levels two to three times higher than those who scored low, Suarez and his colleagues reported in the September issue of the journal Psychosomatic Medicine.
"Most individuals tend to think of heart disease as a condition that is associated with factors such as high cholesterol, high blood pressure, smoking and sedentary lifestyle," Suarez said. "Our findings, however, suggest the development of heart disease may also be due to psychological attributes that activate the inflammatory process shown to predict and contribute to the development of heart disease."
-- Rob Stein
A Key Gene for Green
Chlorophyll is essential for life on Earth. It's the substance that allows green plants to capture energy from the sun and convert it to chemical compounds -- mostly sugars -- in photosynthetic plants. It's perhaps not surprising that such an amazing reaction is a potentially hazardous one.
Seeds germinating underground make a precursor compound, called protochlorophyllide, that is converted into chlorophyll as part of the complicated assembly of "photosynthetic units" that occurs once the seedling emerges into the light.
The danger lies in the fact that the precursor, left to wander freely around a plant cell, can capture light energy but cannot convert it into stable, useful compounds. Instead, it dissipates the energy in tissue-destroying "free radicals," something like setting off a crate of firecrackers. This causes bleaching of plants and sometimes death.
In the current issue of the journal Science, researchers at the University of California at Berkeley and several other institutions shed light on how emerging plants keep this from happening.
Peter H. Quail, Enamul Huq and their colleagues identified a gene, pif1, that directs the germinating seed to make a protein that strictly limits production of the dangerous precursor. Seeds missing the gene made twice as much protochlorophyllide as normal during the dark, underground growth period. They made five times the normal amount in the first few hours after emergence. The result was fatal bleaching.
It appears the pif1 gene is regulated by activation of the light receptors in the photosynthetic assembly. When the receptors are up and running, pif1 backs off, allowing the seedling to crank out billions of molecules of the dangerous precursor, which are immediately converted to chlorophyll molecules and put to work.
-- David Brown