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  3. Once, Plant Breeders dreamed of plumper tomatoes, heartier soybeans, and juicier corn kernels. These days, visions of squat popl

Once, Plant Breeders dreamed of plumper tomatoes, heartier soybeans, and juicier corn kernels. These days, visions of squat popl

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问题     Once, Plant Breeders dreamed of plumper tomatoes, heartier soybeans, and juicier corn kernels. These days, visions of squat poplars and earless corn stalks are dancing in their heads. They are hoping their new fangled crops will make cost-effective biofuels.
    The dominant method of making biofuels today, converting sugars from crops such as corn or sugarcane to ethanol, threatens the food supply and imposes environmental costs. Ultimately, processing cellulose from the cell walls of stems and leaves, which are generally discarded, would make better use of agricultural acreage, as would increasing the oil content of oil-producing crops. In the United States, both government-supported genomicists and privately funded plant scientists are expanding plant genomics research and field studies to figure out the species with the best biofuel potential and how to wring more energy out of each acre planted.
    Many researchers are looking at well-known species whose genomes have already been sequenced for clues to making other plants better energy crops: Arabidopsis, rice, poplar, and now, corn. Others plan to tackle sequencing projects for species few had card about until a few years ago. These include perennials such as switch grass and Miscanthus, both considered good candidates for energy crops because of their high cellulose content. And some scientists are breeding a wide variety of candidate crops around the world, hoping to find optimal varieties. "The spotlight is on this underdeveloped field," says plant biochemist Kenneth Keegstra of Michigan State University in East Lansing, part of the Great Lakes Bioenergy Research Center.
    Humans have been growing food crops for 10,000 years, but the effort to produce fuel down on the farm is in its fancy. Studies of the genetic factors that control cell walls are just reviving up, and key finds have often occurred serendipitously. "We’re at such a basic stage," says Great Lakes center biologist Richard Amasino. For example, in examining why certain varieties of maize showed sugar-rich yellowsplotches—researchers dubbed them "tie-dyed" mutants— plant geneticist David Braun of Pennsylvania State University in State College found abnormal amounts of cellulose accumulating in the mutants’ cell walls—a potentially useful feature in biofuel crops. Braun hypothesizes that the genes involved could be used in grasses to boost their cellulose content. And last year, Keegstra and colleagues described a gene that likely encodes the enzyme that makes one of four hemicelluloses, which along with cellulose and lignin, make up cell walls, in Arabidopsis. Keegstra believes a cell wall engineered to include more hemicellulose might be more easily digestible by biofuel-processing enzymes.
    Keegstra and Amasino’s institute is one of three centers established by the U. S. Department of Energy(DOE), which is providing each $135 million over 5 years to bring genomics to bear on biofuels. Another, the Joint BioEnergy Institute, led by Lawrence Berkeley National Laboratory, will try to find other relevant genes in Arabidopsis and rice. The BioEnergy Science Center at Oak Ridge National Laboratory in Tennessee will focus on poplar and switchgrass.
     (Each includes enzyme scientists and microbiologists chasing better techniques of breaking cellulose down into fermentable sugars.)
In the United States, both genomicists and plant scientists want to find out
选项 A、the way converting sugars from crops such as corn or sugarcane to ethanol.
B、how to process cellulose from the cell walls of stems and leaves.
C、how to increase the oil content of oil-producing crops.
D、how to make high-energy plants.
答案D
解析 推理判断题。由题干关键词genomicists and plant scientists定位至第二段。该段提到bothgovernment-supported genomicists and privately funded plant scientists…wring more energy out of eachacre planted．政府支持的基因组学家和个人资助的植物学家都在开展植物基因组学研究和现场研究，要找到最好的潜在生物燃料种类以及怎样从每亩田当中吸取更多的能量。可见，只要种植高能源的植物，就可在每亩田里吸取更多的能量，故[D]符合题意，为正确答案。由原文吸取更多的能量而并非converting sugars和process cellulose，故排除[A]、[B]；也并非特指oil content，故排除[C]。
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