托福閱讀原文

　　Research has shown that certain mineralsare required by plants for normal growth and development. The soil is thesource of these minerals, which are absorbed by the plant with the water fromthe soil. Even nitrogen, which is a gas in its elemental state, is normallyabsorbed from the soil as nitrate ions. Some soils are notoriously deficient inmicro nutrients and are therefore unable to support most plant life. So-calledserpentine soils, for example, are deficient in calcium, and only plants ableto tolerate low levels of this mineral can survive. In modern agriculture,mineral depletion of soils is a major concern, since harvesting cropsinterrupts the recycling of nutrients back to the soil.

　　Mineral deficiencies can often be detectedby specific symptoms such as chlorosis (loss of chlorophyll resulting in yellowor white leaf tissue), necrosis (isolated dead patches), anthocyanin formation(development of deep red pigmentation of leaves or stem), stunted growth, anddevelopment of woody tissue in an herbaceous plant. Soils are most commonlydeficient in nitrogen and phosphorus. Nitrogen-deficient plants exhibit many ofthe symptoms just described. Leaves develop chlorosis; stems are short andslender, and anthocyanin discoloration occurs on stems, petioles, and lowerleaf surfaces. Phosphorus-deficient plants are often stunted, with leavesturning a characteristic dark green, often with the accumulation ofanthocyanin. Typically, older leaves are affected first as the phosphorus ismobilized to young growing tissue. Iron deficiency is characterized bychlorosis between veins in young leaves.

　　Much of the research on nutrientdeficiencies is based on growing plants hydroponically, that is, in soillessliquid nutrient solutions. This technique allows researchers to createsolutions that selectively omit certain nutrients and then observe theresulting effects on the plants. Hydroponics has applications beyond basicresearch, since it facilitates the growing of greenhouse vegetables duringwinter. Aeroponics, a technique in which plants are suspended and the rootsmisted with a nutrient solution, is another method for growing plants withoutsoil.

　　While mineral deficiencies can limit thegrowth of plants, an overabundance of certain minerals can be toxic and canalso limit growth. Saline soils, which have high concentrations of sodiumchloride and other salts, limit plant growth, and research continues to focuson developing salt-tolerant varieties of agricultural crops. Research hasfocused on the toxic effects of heavy metals such as lead, cadmium, mercury,and aluminum; however, even copper and zinc, which are essential elements, canbecome toxic in high concentrations. Although most plants cannot survive inthese soils, certain plants have the ability to tolerate high levels of theseminerals.

　　Scientists have known for some time thatcertain plants, called hyper accumulators, can concentrate minerals at levels ahundredfold or greater than normal. A survey of known hyper accumulatorsidentified that 75 percent of them amassed nickel, cobalt, copper, zinc,manganese, lead, and cadmium are other minerals of choice. Hyper accumulatorsrun the entire range of the plant world. They may be herbs, shrubs, or trees.Many members of the mustard family, spurge family, legume family,and grass family are top hyper accumulators. Many are found in tropical andsubtropical areas of the world, where accumulation of high concentrations ofmetals may afford some protection against plant-eating insects and microbial pathogens.

　　Only recently have investigators consideredusing these plants to clean up soil and waste sites that have been contaminatedby toxic levels of heavy metals–an environmentally friendly approach known asphytoremediation. This scenario begins with the planting of hyper accumulatingspecies in the target area, such as an abandoned mine or an irrigation pondcontaminated by runoff. Toxic minerals would first be absorbed by roots butlater relocated to the stem and leaves. A harvest of the shoots would removethe toxic compounds off site to be burned or composted to recover the metal forindustrial uses. After several years of cultivation and harvest, the site wouldbe restored at a cost much lower than the price of excavation and reburial, thestandard practice for remediation of contaminated soils. For examples, in fieldtrials, the plant alpine pennycress removed zinc and cadmium from soils near azinc smelter, and Indian mustard, native to Pakistan and India, has beeneffective in reducing levels of selenium salts by 50 percent in contaminatedsoils.

　　托福閱讀試題

　　1. According to paragraph 1, what is trueof plants that can grow in serpentine soil?

　　A.They absorb micronutrients unusuallywell.

　　B.They require far less calcium than mostplants do.

　　C.They are able to absorb nitrogen in itselemental state.

　　D.They are typically crops raised for food.

　　2. The word “exhibit”in the passage(paragraph 2) is closest in meaning to

　　A. fight off

　　B. show

　　C.cause

　　D.spread

　　3. According to paragraph 2, which of thefollowing symptoms occurs in phosphorus-deficient plants but not in plantsdeficient in nitrogen or iron?

　　A.Chlorosis on leaves

　　B.Change in leaf pigmentation to a darkshade of green

　　C.Short, stunted appearance of stems

　　D.Reddish pigmentation on the leaves orstem

　　4. According to paragraph 2, a symptom ofiron deficiency is thepresence in young leaves of

　　A.deep red discoloration between the veins

　　B.white or yellow tissue between the veins

　　C.dead spots between the veins

　　D.characteristic dark green veins

　　5. The word “facilitates”in the passage(paragraph 3) is closest in meaning to

　　A.slows down

　　B. affects

　　C. makes easier

　　D. focuses on

　　6. According to paragraph 3, what is theadvantage of hydroponics forresearch on nutrient deficiencies in plants?

　　A.It allows researchers to control whatnutrients a plant receives.

　　B.It allows researchers to observe thegrowth of a large number of plants simultaneously.

　　C.It is possible to directly observe theroots of plants.

　　D.It is unnecessary to keep misting plantswith nutrient solutions.

　　7. The word “suspended”in the passage(paragraph 3) is closest in meaning to

　　A.grown

　　B.protected

　　C.spread out

　　D.hung

　　8. Why does the author mention “herbs”, “shrubs”,and “trees”? (paragraph 5)

　　A.To provide examples of plant types thatcannot tolerate high levels of harmful minerals.

　　B.To show why so many plants are hyperaccumulators.

　　C.To help explain why hyper accumulatorscan be found in so many different places.

　　D.To emphasize that hyper accumulatorsoccur in a wide range of plant types.

　　9. The word “afford”in the passage(paragraph 5) is closest in meaning to

　　A.offer

　　B.prevent

　　C.increase

　　D.remove

　　10. Which of the sentences below bestexpresses the essential information in the highlighted sentence in the passage(paragraph 6)? Incorrect choices change the meaning in important ways or leaveout essential information.

　　A.Before considering phytoremediation, hyperaccumulating species of plants local to the target area must be identified.

　　B.The investigation begins with anevaluation of toxic sites in the target area to determine the extent ofcontamination.

　　C.The first step in phytoremediation is theplanting of hyper accumulating plants in the area to be cleaned up.

　　D.Mines and irrigation ponds can be keptfrom becoming contaminated by planting hyper accumulating species in targetedareas.

　　11. It can be inferred from paragraph6 thatcompared with standard practices for remediation of contaminated soils,phytoremediation

　　A.does not allow for the use of the removedminerals for industrial purposes

　　B.can be faster to implement

　　C.is equally friendly to the environment

　　D.is less suitable for soils that need tobe used within a short period of time

　　12. Why does the author mention “Indianmustard”? (paragraph 6)

　　A.To warn about possible risks involved inphytoremediation

　　B.To help illustrate the potential of phytoremediation

　　C.To show that hyper accumulating plantsgrow in many regions of the world

　　D.To explain how zinc contamination can bereduced

　　13. Look at the four squares [■]that indicate where the following sentence could be added to the passage. Certainminerals are more likely to be accumulated in large quantities than others.

　　Scientists have known for some time thatcertain plants, called hyper accumulators, can concentrate minerals at levels ahundredfold or greater than normal. ■ 【A】A survey ofknown hyper accumulators identified that 75 percent of them amassed nickel,cobalt, copper, zinc, manganese, lead, and cadmium are other minerals ofchoice. ■ 【B】Hyper accumulators run the entire range of the plant world. ■ 【C】They may beherbs, shrubs, or trees. ■ 【D】Many members of the mustard family, spurge family, legumefamily, and grass family are top hyper accumulators. Many are found in tropicaland subtropical areas of the world, where accumulation of high concentrationsof metals may afford some protection against plant-eating insects and microbialpathogens.

　　Where could the sentence best fit?

　　14. Directions: An introductory sentencefor a brief summary of the passage is provided below. Complete the summary byselecting the THREE answer choices that express the most important ideas in thepassage. Some answer choices do not belong in the summary because they expressideas that are not presented in the passage or are minor ideas in the passage.This question is worth 2 points.

　　Plants need to absorb certain minerals fromthe soil in adequate quantities for normal growth and development.

　　A.Some plants are able to accumulateextremely high levels of certain minerals and thus can be used to clean upsoils contaminated with toxic levels of these minerals.

　　B.Though beneficial in lower levels, highlevels of salts, other minerals, and heavy metals can be harmful to plants.

　　C.When plants do not absorb sufficientamounts of essential minerals, characteristic abnormalities result.

　　D.Because high concentrations of sodiumchloride and other salts limit growth in most plants, much research has beendone in an effort to develop salt-tolerant agricultural crops.

　　E.Some plants can tolerate comparativelylow levels of certain minerals, but such plants are of little use for recyclingnutrients back into depleted soils.

　　F.Mineral deficiencies in many plants canbe cured by misting their roots with a nutrient solution or by transferring theplants to a soilless nutrient solution.

　　托福閱讀答案

　　1. 以serpentine soil做關(guān)鍵詞定位至倒數(shù)第二句，這種土壤鈣質(zhì)缺乏，只有對(duì)鈣要求很低的植物可以生存。問題問什么樣的植物能夠生存，所以B正確。A中micronutrients沒說，C的nitrogen和elemental state與問題無關(guān)，錯(cuò);D的food沒說

　　2. exhibit顯示，顯出，所以B的show正確。原句說氮缺乏的植物怎么樣很多現(xiàn)象，所以是顯示很多現(xiàn)象，MS引起很多現(xiàn)象也對(duì)，但不一定能把氮缺乏和那些現(xiàn)象聯(lián)系起來，所以因果關(guān)系有些牽強(qiáng)，剩下的A斗爭D蔓延完全不對(duì)

　　3.以phosphorus-deficientplants做關(guān)鍵詞定位至倒數(shù)第二句，說phosphorus-deficient，磷缺乏的植物是容易倒的，并且葉子會(huì)變成暗綠色，B是答案。A中的chlorosis萎黃病，變色病沒說;C中的莖很短原文沒說;D中的reddish pigmentation原文沒說

　　4.以iron deficiency和young leaves做關(guān)鍵詞定位至最后一句，chlorosis變色病，萎黃病，所以B項(xiàng)的white oryellow tissue剛好對(duì)上。A項(xiàng)的deep red沒說，錯(cuò);C的dead spots原文沒說，錯(cuò);D的dark green是缺乏磷的癥狀，不對(duì)

　　5. facilitate促進(jìn)，幫助，使變?nèi)菀祝�所以C的makes easier正確。原句說hydroponic除了基本研究之外還有其他應(yīng)用，就是實(shí)際上的應(yīng)用，說怎么樣了冬天里溫室蔬菜的生長。從感情色彩上看，這個(gè)地方要的是一個(gè)正向詞，A的slow down和B的affect都不對(duì)。只是focus on還不行，必須正向，所以答案是make easier

　　6.以nutrient deficiency做關(guān)鍵詞定位至第一句，但第一句只是給這個(gè)無土栽培下了個(gè)定義，第二句才開始說好處，使得researchers能夠有意去掉某種營養(yǎng)，然后看效果，也就是A說的可以選擇讓植物吸收什么營養(yǎng);其他三項(xiàng)都完全沒說

　　7. suspend懸垂，懸掛，所以hung是正確答案。原句中acroponics意思是空氣種植法，acro表示懸空，所以后面的解釋是把植物怎么樣，而且跟后面的mist并列，mist混合�；旌吓c成長是不能并列的，grow錯(cuò);同樣spring長出來也不對(duì);protect是完全不靠譜的

　　8.修辭目的題，而且這句話中有個(gè)they，指代前文，所以往前看，說HA在整個(gè)植物界分布廣泛，后面的幾種植物就是HA的例子，所以答案是D。A說cannot tolerate反了;原文沒說到原因，所以B/C都錯(cuò)

　　9. afford買得起，能承受，所以offer提供，給出是正確答案。很多物種都生長在熱帶及亞熱帶地區(qū)，那兒的高濃度金屬可以怎么樣保護(hù)植物免遭吃植物的昆蟲的捕食。B的prevent防止保護(hù)和D的remove去除保護(hù)肯定不對(duì);increase增加保護(hù)是在原有的基礎(chǔ)上增加，原文沒說原來就有保護(hù)，所以increase不對(duì)

　　10.原句的結(jié)構(gòu)是這件事開始于blabla在某地，比如blabla地區(qū);A中的before是沒說的，原文一直在說這件事開始于什么什么，這件事之前干嘛沒說;原文有個(gè)很難替換的詞HAS，而這個(gè)詞在B答案中沒有，所以B 錯(cuò);C同義替換，正確;D把such as里面的例子變成了句子的主要部分，改變了結(jié)構(gòu)，錯(cuò)

　　11.以contaminated soil和remediation做關(guān)鍵詞定位至倒數(shù)第二句，說經(jīng)過若干年的耕種與收割之后，那個(gè)地方就會(huì)恢復(fù)，說明沒有若干年就不能恢復(fù)，所以D正確。A/C沒有相關(guān)信息;B說反，應(yīng)該是傳統(tǒng)的挖掘方法更快，新的種植物的方法慢

　　12.修辭目的題，Indian mustard做關(guān)鍵詞定位至最后一句，這句話整個(gè)是個(gè)例子，而且之前的那句話也是個(gè)例子。再往前就是上題的那句話，也就是說經(jīng)過若干年耕種與收割，那個(gè)地方就會(huì)變好，也就是這種方法有用，所以答案B正確

　　13.三個(gè)過渡點(diǎn)，certainminerals，large quantities和代詞others，有mineral的只有A和B兩個(gè)選項(xiàng);帶入之后發(fā)現(xiàn)A是正確的，待插入句說有的礦物比別的礦物更容易沉積，而原文的第二句是對(duì)待插入句的一種解釋，所以應(yīng)該放在待插入句之后，所以A對(duì)B錯(cuò)

　　14. some plants are選項(xiàng)對(duì)應(yīng)原文第五段和第六段的第一句，正確

　　though選項(xiàng)對(duì)應(yīng)原文第四段第一句，正確

　　when選項(xiàng)對(duì)應(yīng)原文第二段第一句，正確

　　because選項(xiàng)中的因果關(guān)系原文沒說，而且氯化鈉也是個(gè)細(xì)節(jié)，不選

　　some plants can選項(xiàng)是第一段的一個(gè)細(xì)節(jié)，不選

　　mineral deficiency選項(xiàng)是原文第三段的一個(gè)細(xì)節(jié)，不選