对于托福阅读的备考，同学们最重要就是要多练习，除了了解托福阅读考试的特点和适应托福阅读考试的考试形式，还可以增强做题语感，因为阅读题目最重要的就是语感。下面新航道托福小编跟大家分享托福阅读TPO4真题及答案： MINERALS AND PLANTS，供大家练习参考：

　　托福阅读TPO4：MINERALS AND PLANTS

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

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

　　Much of the research on nutrient　deficiencies is based on growing plants　hydroponically, that is, in soilless liquid　nutrient solutions. This technique allows　researchers to create solutions that　selectively omit certain nutrients and then observe the resulting effects on the　plants. Hydroponics has applications　beyond basic research, since it facilitates　the growing of greenhouse vegetables during winter. Acroponics, a technique in　which plants are suspended and the roots　misted with a nutrient solution, is another　method for growing plants without soil.

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

　　Scientists have known for some　time that certain plants, called hyper　accumulators, can concentrate minerals　at levels a hundredfold or greater than　normal. A survey of known hyper　accumulators identified that 75 percent　of them amassed nickel, cobalt, copper,zinc, manganese, lead, and cadmium are other minerals of choice. Hyper　accumulators run 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　and subtropical areas of the world, where　accumulation of high concentrations of　metals may afford some protection　against plant-eating insects and microbial　pathogens.

　　Only recently have investigators　considered using these plants to clean up　soil and waste sites that have been　contaminated by toxic levels of heavy　metals - an environmentally friendly　approach known as phytoremediation.This scenario begins with the planting of　hyper accumulating species in the target　area, such as an abandoned mine or an　irrigation pond contaminated by runoff.Toxic minerals would first be absorbed　by roots but later relocated to the stem　and leaves. A harvest of the shoots would　remove the toxic compounds off site to　be burned or composted to recover the　metal for industrial uses. After several　years of cultivation and harvest, the site　would be restored at a cost much lower　than the price of excavation and reburial,　the standard practice for remediation of　contaminated soils. For examples, in field trials, the plant alpine pennycress　removed zinc and cadmium from soils　near a zinc smelter, and Indian mustard,native to Pakistan and India, has been　effective in reducing levels of selenium　salts by 50 percent in contaminated soils.

　　Paragraph1:

　　1. According to Paragraph1, what is true of　plants that can grow in serpentine soil

　　They absorb micronutrients unusually well.

　　They require far less calcium than most plants do.

　　They are able to absorb nitrogen in its elemental state.

　　They are typically crops raised for food.

　　Paragraph2:

　　2. The word exhibit in the passage is　closest in meaning to

　　fight off

　　show

　　cause

　　spread

　　3. According to Paragraph2, which of the　following symptoms occurs in phosphorus-deficient plants but not in plants deficient in nitrogen or iron

　　Chlorosis on leaves in leaf pigmentation to a dark shade of green

　　Short, stunted appearance of stems

　　Reddish pigmentation on the leaves or stem

　　Change

　　4. According to Paragraph2, a symptom of iron deficiency is the presence in young leaves of

　　Deep red discoloration between the veins.

　　White or yellow tissue between the veins.

　　Dead spots between the veins.

　　Characteristic dark green veins.

　　Paragraph3:

　　5. The word facilitates in the passage is closest in meaning to

　　slows down

　　affects

　　makes easier

　　focuses on

　　6. According to Paragraph3, what is the advantage of hydroponics for research on nutrient deficiencies in plants

　　It allows researchers to control what nutrients a plant receives.

　　It allows researchers to observe the growth of a large number of plants simultaneously.

　　It is possible to directly observe the roots of plants.

　　It is unnecessary to keep misting plants with nutrient solutions.

　　7. The word suspended in the passage is closest in meaning to

　　grown

　　protected

　　spread out

　　hung

　　Paragraph5:

　　8. Why does the author mention herbs,shrubs, and trees

　　To provide examples of plant types that cannot tolerate high levels of harmful minerals.

　　To show why so many plants are hyper accumulators.

　　To help explain why hyper accumulators can be found in so many different places.

　　To emphasize that hyper accumulators occur in a wide range of plant types.

　　9. The word afford in the passage is closest in meaning to

　　offer

　　prevent

　　increase

　　remove

　　Paragraph 6:

　　10. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage Incorrect choices change the meaning in important ways or leave out essential information.

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

　　The investigation begins with an evaluation of toxic sites in the target area to determine the extent of contamination.

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

　　Mines and irrigation ponds can be kept from becoming contaminated by planting hyper accumulating species in targeted areas.

　　11. It can be inferred from Paragraph6 that compared with standard practices for remediation of contaminated soils,phytoremediation

　　does not allow for the use of the removed minerals for industrial purposes.

　　can be faster to implement equally friendly to the environment

　　is less suitable for soils that need to be used within a short period of time.

　　12. Why does the author mention Indian mustard

　　To warn about possible risks involved in phytoremediation

　　To help illustrate the potential of phytoremediation

　　To show that hyper accumulating plants grow in many regions of the world

　　To explain how zinc contamination can be reduced.

　　Paragraph7:

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

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

　　Answer Choices

　　1. Some plants are able to accumulate extremely high levels of certain minerals and thus can be used to clean up soils contaminated with toxic levels of these minerals.

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

　　3. When plants do not absorb sufficient amounts of essential minerals, characteristic abnormalities result.

　　4. Because high concentrations of sodium chloride and other salts limit growth in most plants, much research has been done in an effort to develop salt-tolerant agricultural crops.

　　5. Some plants can tolerate comparatively low levels of certain minerals, but such plants are of little use for recycling nutrients back into depleted soils.

　　6. Mineral deficiencies in many plants can be cured by misting their roots with a nutrient solution or by transferring the plants to a soilless nutrient solution.

　　托福TPO04 MINERALS AND PLANTS参考答案：

　　1.○2 2.○2 3.○2 4.○2 5.○3

　　6.○1 7.○4 8.○4 9.○1 10.○3

　　11.○4 12.○2 13.○1 14.○1 2 3

　　以上就是新航道托福小编跟大家分享的关于一篇托福阅读TOP及答案，希望对大家有所帮助！最后预祝大家在托福考试中取得好成绩！