C.Live Better on Less D.What's Your Home Longing to Tell You?

2.This tip sheet is intended to　　　.

A.write better course descriptions

B.make instructors' life colorful

C.support the community programs

D.promote effective learning

　　Recent summer temperatures in parts of Australia were high enough to melt asphalt. As global warming speeds up the heat and climatic events increase, many plants may be unable to cope. But at least one species of eucalyptus tree can resist extreme heat by continuing to "sweat" when other essential processes stop, a new study finds.

　　As plants change sunlight into food, or photosynthesize(进行光合作用), they absorb carbon dioxide through pores on their leaves. These pores also release water via transpiration(蒸腾), which circulates nutrients through the plant and helps cool it by evaporation(蒸发). But exceptionally high temperatures are known to greatly reduce photosynthesis-and most existing plant models suggest this should also decrease transpiration, leaving trees in danger of fatally overheating. Because it is difficult for scientists to control and vary trees' conditions in their natural environment, little is known about how individual species handle this situation.

　　Ecologist John Drake of the S.U.N.Y. College of Environmental Science and Forestry and his colleagues grew a dozen Parramatta red gum(Eucalyptus parramattensis) trees in large, climate-controlled plastic pods that separated the trees from the surrounding forest for a year in Richmond, Australia. Six of the trees were grown at surrounding air temperatures and six at temperatures three degrees Celsius higher. The researchers withheld (扣留) water from the surface soil of all 12 trees for a month to imitate a mild dry spell, then induced a four-day "extreme" heat wave:They raised the maximum temperatures in half of the pods(three with surrounding temperatures and three of the warmer ones)-to 44 degrees C.

Photosynthesis ground to a near halt in the trees facing the artificial heat wave. But to the researchers' surprise, these trees continued to transpire at close-to-normal levels, effectively cooling themselves and their surroundings. The trees grown in warmer conditions coped just as