英语听力文摘 English Digest 244、光呼吸作用之谜

　　The Mystery of Photorespiration
光呼吸作用之谜
光呼吸作用-Photorespiration是所有行光合作用的细胞（该处“细胞”包括原核生物和真核生物，但并非所有这些细胞都能运行完整的光呼吸）在光照和高氧低二氧化碳情况下发生的一个生化过程。它是光合作用一个损耗能量的副反应。过程中氧气被消耗，并且会生成二氧化碳光呼吸作用ht约抵消30%的光合作用。因此降低光呼吸被认为是提高光合作用效能的途径之一。但是人们后来发现，光呼吸作用有着很重要的细胞保护作用。
Today, we’re talking about plants and the mystery of photorespiration, which is actually diametrically opposed to photosynthesis¹.
It is the process by which plants use light to convert carbon dioxide and water into the sugars that fuel the plant，right？
Right，Well, during photorespiration plants use light energy to consume oxygen and release carbon dioxide and water.
So photorespiration undoes² the work of photosynthesis？
At least part of it，so under present atmospheric³ conditions, plants lose about twenty-five percent of the energy that they capture through photosynthesis to photorespiration.
One hypothesis is that photorespiration had a role in early evolution, when there was more carbon dioxide in the air. Another explanation is that plants use photorespiration to slow down photosynthesis under certain stressful conditions, like intense light, so that the photosynthetic⁴ apparatus⁵ doesn’t get damaged.

　　Given all the mystery surrounding this process, some scientists even began working on genetically⁶ engineering crop plants to minimize photorespiration. But one study suggests that photorespiration is actually important to plants after all.
Researchers at UC Davis showed that photorespiration enables a plant to convert inorganic⁷ nitrogen into a form of nitrate that’s needed for plant growth. This helps explain why plants have trouble growing in conditions with low oxygen and high carbon dioxide, which inhibit⁸ photorespiration.
Notes
1.convert v
改变（某事物）的形式或用途:
Britain converted to a decimal currency system in 1971. 英国於1971年改行十进制货币体系.
a ferry that was converted to carry troops during the war 战争期间改作运兵船的渡轮
The room was converted from a kitchen to a lavatory⁹. 这房间由厨房改成了厕所.
~ into/to sth: be able to be changed from one form or use to another 可改变形式或用途:
a sofa that converts (in) to a bed 可改为床铺的沙发.
2.minimize, minimise  v
使（某事物）减至最小量或最低程度:
To minimize the risk of burglary, install a good alarm system. 安装可靠的报警设备以减低被盗的风险.

1 photosynthesis   

n.光合作用

参考例句：

• In apple trees photosynthesis occurs almost exclusively in the leaves.苹果树的光合作用几乎只发生在叶内。
• Chloroplasts are the structures in which photosynthesis happens.叶绿体就是光合作用发生的地方。

2 undoes   

松开( undo的第三人称单数 )； 解开； 毁灭； 败坏

参考例句：

• Undoes the last action or a sequence of actions, which are displayed in the Undo list. 撤消上一个操作或者一系列操作，这些操作显示在“撤消”列表中。

3 atmospheric   

adj.大气的，空气的；大气层的；大气所引起的

参考例句：

• Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
• Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。

4 photosynthetic   

adj.光合的，促进光合作用的

参考例句：

• In some plants photosynthetic products are stored in the form polyfructosans. 在有些植物中，光合作用产物是以多聚果糖的形式储藏。
• Chlorotic or necrotic lesions were evidence of decreased photosynthetic tissues. 缺绿的或坏死的侵蚀斑便是减少了光合组织的证据。

5 apparatus   

n.装置，器械；器具，设备

参考例句：

• The school's audio apparatus includes films and records.学校的视听设备包括放映机和录音机。
• They had a very refined apparatus.他们有一套非常精良的设备。

6 genetically   

adv.遗传上

参考例句：

• All the bees in the colony are genetically related. 同一群体的蜜蜂都有亲缘关系。
• Genetically modified foods have already arrived on American dinner tables. 经基因改造加工过的食物已端上了美国人的餐桌。 来自英汉非文学 - 生命科学 - 基因与食物

7 inorganic   

adj.无生物的；无机的

参考例句：

• The fundamentals of inorganic chemistry are very important.无机化学的基础很重要。
• This chemical plant recently bought a large quantity of inorganic salt.这家化工厂又买进了大量的无机盐。

8 inhibit   

vt.阻止，妨碍，抑制

参考例句：

• Don't let ego and greed inhibit clear thinking and hard work.不要让自我和贪婪妨碍清晰的思维和刻苦的工作。
• They passed a law to inhibit people from parking in the street.他们通过一项法令以阻止人们在街上停车。

9 lavatory   

n.盥洗室，厕所

参考例句：

• Is there any lavatory in this building?这座楼里有厕所吗？
• The use of the lavatory has been suspended during take-off.在飞机起飞期间，盥洗室暂停使用。