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  3. About fifty years ago, plant physiologists set out to grow roots by themselv

About fifty years ago, plant physiologists set out to grow roots by themselv

游客2023-12-31  3
问题     About fifty years ago, plant physiologists set out to grow roots by themselves in solutions in laboratory flasks. The scientists found that the nutrition of isolated roots was quite simple. They required sugar and the usual minerals and vitamins. However, they did not require organic nitrogen compounds. These roots got along free on mineral inorganic nitrogen. Roots are capable of making their own proteins and other organic compounds. These activities by roots require energy, of course. The process of respiration uses sugar to make the high energy compound ATP, which drives the biochemical reactions. Respiration also requires oxygen. Highly active roots require a good deal of oxygen.
    The study of isolated roots has provided an understanding of the relationship between shoots and roots in intact plants. The leaves of the shoots provide the roots with sugar and vitamins, and the roots provide the shoots with water and minerals. In addition, roots can provide the shoots with organic nitrogen compounds. This comes in handy for the growth of buds in the early spring when leaves are not yet functioning. Once leaves begin photosynthesizing, they produce protein, but only mature leaves can "export" protein to the rest of the plant in the form of amino acids. [br] The underlined word "intact" in Paragraph 2 is closest in meaning to______.
选项 A、mature
B、wild
C、whole
D、tiny
答案 C
解析 本题考查词义理解。解题点在于第二段第一句“The study of isolated roots has pro—vided an understanding of the relationship between shoots and roots in intact plants．”，句意为：对于分离出的根所做的研究提供了对完整植物中根和芽的关系的理解。intact“完整的”；mature“成熟的”；wild“野生的”；whole“整体的”；tiny“微小的”。比较可知，答案是C。
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