二氧化碳能增加食欲

Carbon dioxide is a potent greenhouse gas. Levels of carbon dioxide, or CO2, in the atmosphere are increasing at an unprecedented rate. But what impact do higher CO2 levels have on plants? Plants use CO2 from the air along with sunlight and water to produce carbohydrates they use for energy. This process is called photosynthesis. Higher atmospheric CO2 increases the rate of photosynthesis, and thus the amount of carbohydrates in plant leaves. Sounds beneficial, right? However, scientists have found that as CO2 levels go up, plant defenses might go down. Researchers at the University of Illinois used a special open-air research facility that allowed them to grow soybean plants in different concentrations of CO2—without changing other factors such as sunlight, insects or rainfall. They discovered that soybeans grown in fields with higher CO2 levels had much more insect damage and attracted more adult insect pests than those in plots with less CO2 in the air. The insects might have been attracted by the higher carbohydrate levels in the leaves of plants grown in high CO2. But a higher carb diet wasn’t the only thing that encouraged infestation. Normally, soybean plants under attack by insects will produce jasmonic acid. This inhibits the insects’ ability to digest leaves, which protects the plant from further attack. In high CO2 atmospheres, the plants were unable to produce this defensive chemical. So, the dangers of rapidly increasing CO2 in our atmosphere might extend beyond climate change. Since soybeans grown at higher CO2 would lose a crucial defense pathway and attract more hungry beetles, other food crops might also be more vulnerable if CO2 levels continue to rise.