英語(yǔ)聽(tīng)力文摘光呼吸作用之謎

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The Mystery of Photorespiration

光呼吸作用之謎

光呼吸作用-Photorespiration是所有行光合作用的細(xì)胞(該處“細(xì)胞”包括原核生物和真核生物，但并非所有這些細(xì)胞都能運(yùn)行完整的光呼吸)在光照和高氧低二氧化碳情況下發(fā)生的一個(gè)生化過(guò)程。它是光合作用一個(gè)損耗能量的副反應(yīng)。過(guò)程中氧氣被消耗，并且會(huì)生成二氧化碳光呼吸作用ht約抵消30%的光合作用。因此降低光呼吸被認(rèn)為是提高光合作用效能的途徑之一。但是人們后來(lái)發(fā)現(xiàn)，光呼吸作用有著很重要的細(xì)胞保護(hù)作用。

Today, we’re talking about plants and the mystery of photorespiration, which is actually diametrically opposed to photosynthesis.

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 undoes the work of photosynthesis?

At least part of it，so under present atmospheric 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 photosynthetic apparatus doesn’t get damaged.

Given all the mystery surrounding this process, some scientists even began working on genetically 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 inorganic 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 inhibit photorespiration.

Notes

1.convert v

改變(某事物)的形式或用途:

Britain converted to a decimal currency system in 1971. 英國(guó)於1971年改行十進(jìn)制貨幣體系.

a ferry that was converted to carry troops during the war 戰(zhàn)爭(zhēng)期間改作運(yùn)兵船的渡輪

The room was converted from a kitchen to a lavatory. 這房間由廚房改成了廁所.

~ into/to sth: be able to be changed from one form or use to another 可改變形式或用途:

a sofa that converts (in) to a bed 可改為床鋪的沙發(fā).

2.minimize, minimise v

使(某事物)減至最小量或最低程度:

To minimize the risk of burglary, install a good alarm system. 安裝可靠的報(bào)警設(shè)備以減低被盜的風(fēng)險(xiǎn).

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