题目内容
12．Like people，plants experience stress．And also，like people，the response to that stress can determine success．Bad environmental conditions，such as drought，flood，heat and other stresses，affect yields（产量） more than crop pests and diseases．We are trying to find a way to equip plants with the ability to tolerate environmental stress and maintain high yields，said Stephen Howell，a professor of genetics and cell biology．
Plant cells produce proteins （蛋白质） and ship them to different parts of the cell．Under normal conditions，these proteins are folded into their normal，healthy structures as they are produced．When a plant is under stress，its cells produce poorly folded or unfolded proteins．Then a built-in system senses this and"sets off an alarm in the cell，"said Howell．
In response to the alarm，another protein （IRE1）starts working and creates a different process which activates （激活） the stress response genes whose products bring about defensive measures that help the plant survive．
"As it turns out，responses that are activated under stress conditions actually inhibit the growth of plants，"said Howell．"This allows them to preserve their energy to survive the stress conditions．"
For plants in the wild，this response is a help for survival，he said．In production of agriculture crops，however，this response reduces yields．
"You don't want crop plants to stop growing，"Howell said．"You want them to continue to grow and produce even though they are under stress．"
With the new understanding of this stress response，the next step may be to silence the alarm system，said Howell．"What may be important is to disable some of these stress responses．That may make the plant more productive under stress conditions．"
28．According to the text，an alarm in the plant cells is caused byB．
A．the folded proteins
B．the changed proteins
C．the defensive measures
D．the stress response genes
29．The energy preserved in the plants under stress conditionsA．
A．helps the plants to survive
B．helps to maintain high yields
C．keeps the plants growing
D．helps to produce proteins
30．The underlined word"inhibit"in Paragraph 5can be replaced by"A"．
A．prevent
B．start
C．continue
D．promote
31．How does Howell intend to make crop plants maintain high yields under stress conditions？C
A．By making crop plants keep more energy．
B．By making crop plants stop growing．
C．By making the alarm system stop working．
D．By making the alarm system respond quickly．
分析 本文属于说明文阅读，作者通过这篇文章主要向我们描述了植物细胞的报警是由改变蛋白质产生的，豪厄尔在压力条件下通过使报警系统停止工作使作物保持高产．
解答 28．B．细节理解题．根据第三段：When a plant is under stress，its cells produce poorly folded or unfolded proteins可知植物细胞的报警是由改变蛋白质产生的；故选B．
29．A．细节理解题．根据第四段：another protein （IRE1）starts working and creates a different process which activates （激活） the stress response genes whose products bring about defensive measures that help the plant survive可知胁迫条件下植物的能量保存帮助植物生存；故选A．
30．A．词义理解题．根据第五段：As it turns out，responses that are activated under stress conditions actually inhibit the growth of plants事实证明，在压力条件下被激活的反应实际上抑制了植物的生长，可知意为阻止；故选A．
31．C．细节理解题．根据最后一段：What may be important is to disable some of these stress responses．That may make the plant more productive under stress conditions可知豪厄尔在压力条件下通过使报警系统停止工作使作物保持高产；故选C．
点评 考察学生的细节理解和推理判断能力，做细节理解题时一定要找到文章中的原句，和题干进行比较，再做出正确的选择．在做推理判断题不要以个人的主观想象代替文章的事实，要根据文章事实进行合乎逻辑的推理判断．
