Official5托福阅读Passage1 Minerals and Plants文本+题目原文+答案解析【雷哥托福】2019-01-16 14:34:08 发布 来源：雷哥托福
TPO5托福阅读Passage1 Minerals and Plants文本+题目文本+答案解析
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, is 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 tissue), 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. Aeroponics, 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 hyperaccumulators, can concentrate minerals at levels a hundredfold or greater than normal. [■] A survey of known hyperaccumulators identified that 75 percent of them amassed nickel, cobalt, copper, zinc, manganese, lead, and cadmium are other minerals of choice. [■] Hyperaccumulators 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 hyperaccumulators. [■] 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 hyperaccumulating 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.
TPO5托福阅读Passage1Minerals and Plants题目
Question 1 of 14：According to paragraph 1, what is true of plants that can grow in serpentine soil?
A. They absorb micronutrients unusually well.
B. They require far less calcium than most plants do.
C. They are able to absorb nitrogen in its elemental state.
D. They are typically crops raised for food.
Question 2 of 14：The word “exhibit ” in the passage is closest in meaning to
A. fight off
Question 3 of 14：According to paragraph 2, which of the following symptoms occurs in phosphorus-deficient plants but not in plants deficient in nitrogen or iron?
A. Chlorosis on leaves
B. Change in leaf pigmentation to a dark shade of green
C. Short, stunted appearance of stems
D. Reddish pigmentation on the leaves or stem
Question 4 of 14：According to paragraph 2, a symptom of iron deficiency is the presence 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
Question 5 of 14：The word “facilitates ” in the passage is closest in meaning to
A. slows down
C. makes easier
D. focuses on
Question 6 of 14：According to paragraph 3, what is the advantage of hydroponics for research on nutrient deficiencies in plants?
A. It allows researchers to control what nutrients a plant receives.
B. It allows researchers to observe the growth of a large number of plants simultaneously.
C. It is possible to directly observe the roots of plants.
D. It is unnecessary to keep misting plants with nutrient solutions.
Question 7 of 14：The word “suspended ” in the passage is closest in meaning to
C. spread out
Question 8 of 14：Why does the author mention “herbs”, “shrubs”, and “trees”?
A. To provide examples of plant types that cannot tolerate high levels of harmful minerals.
B. To show why so many plants are hyperaccumulators.
C. To help explain why hyperaccumulators can be found in so many different places.
D. To emphasize that hyperaccumulators occur in a wide range of plant types.
Question 9 of 14：The word “afford ” in the passage is closest in meaning to
Question 10 of 14：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.
A. Before considering phytoremediation, hyperaccumulating species of plants local to the target area must be identified.
B. The investigation begins with an evaluation of toxic sites in the target area to determine the extent of contamination.
C. The first step in phytoremediation is the planting of hyperaccumulating plants in the area to be cleaned up.
D. Mines and irrigation ponds can be kept from becoming contaminated by planting hyperaccumulating species in targeted areas.
Question 11 of 14：It can be inferred from paragraph 6 that compared with standard practices for remediation of contaminated soils, phytoremediation
A. does not allow for the use of the removed minerals for industrial purposes
B. can be faster to implement
C. is equally friendly to the environment
D. is less suitable for soils that need to be used within a short period of time
Question 12 of 14：Why does the author mention “Indian mustard ”?
A. To warn about possible risks involved in phytoremediation
B. To help illustrate the potential of phytoremediation
C. To show that hyperaccumulating plants grow in many regions of the world
Question 13 of 14：Look at the four squares [■] that indicate where the following sentence could be added to the passage.Where could the sentence best fit?
Certain minerals are more likely to be accumulated in large quantities than others.
A. A survey of known hyperaccumulators identified that 75 percent of them amassed nickel, cobalt, copper, zinc, manganese, lead, and cadmium are other minerals of choice.
B. Hyperaccumulators run the entire range of the plant world.
C. They may be herbs, shrubs, or trees. Many members of the mustard family, spurge family, legume family, and grass family are top hyperaccumulators.
D. 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.
Question 14 of 14：Directions: An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some answer choices do not belong in the summary because they express ideas 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 from the soil in adequate quantities for normal growth and develop
A.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.
B.Though beneficial in lower levels, high levels of salts, other minerals, and heavy metals can be harmful to plants.
C.When plants do not absorb sufficient amounts of essential minerals, characteristic abnormalities result.
D.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.
E.Some plants can tolerate comparatively low levels of certain minerals, but such plants are of little use for recycling nutrients back into depleted soils.
F. 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.
TPO5托福阅读Passage1Minerals and Plants答案解析
Question 1 of 14
题目解析：以serpentine soil做关键词定位至倒数第二句，这种土壤钙质缺乏，只有对钙要求很低的植物可以生存。问题问什么样的植物能够生存，所以B正确。A中micronutrients没说，C的nitrogen和elemental state与问题无关，错;D的food没说。
Question 2 of 14
Question 3 of 14
题目解析：以phosphorus-deficient plants做关键词定位至倒数第二句，说phosphorus-deficient，磷缺乏的植物是容易倒的，并且叶子会变成暗绿色，B是答案。A中的chlorosis萎黄病，变色病没说;C中的茎很短原文没说;D中的reddish pigmentation原文没说。
Question 4 of 14
题目解析：以iron deficiency和young leaves做关键词定位至最后一句，chlorosis变色病，萎黄病，所以B项的white or yellow tissue刚好对上。A项的deep red没说，错;C的dead spots原文没说，错;D的dark green是缺乏磷的症状，不对。
Question 5 of 14
题目解析：facilitate: 促进，帮助，使容易。A是变慢;B是影响;C是使容易;D是集中于。所以C的makes easier正确。对应原文:Hydroponics has applications beyond basic research, since it facilitates the growing of greenhouse vegetables during winter. 原句说hydroponic除了基本研究之外还有其他应用，就是实际上的应用，说怎么样了冬天里温室蔬菜的生长。从感情色彩上看，这个地方要的是一个正向词，A的slow down和B的affect都不对。focus on也不行，属于中性词，必须正向，所以答案是make easier。
Question 6 of 14
题目解析：以nutrient deficiency做关键词定位至第一句，但第一句只是给这个无土栽培下了个定义，第二句才开始说好处：This technique allows researchers to create solutions that selectively omit certain nutrients and then observe the resulting effects on the plants.使得researchers能够有意去掉某种营养，然后看效果，也就是A说的可以选择让植物吸收什么营养;其他三项都完全没说。
Question 7 of 14
题目解析：suspend: 悬垂，悬挂。A是种植;B是保护;C是展开，铺开;D是悬挂。所以D的hung是正确答案。对应原文:Aeroponics, a technique in which plants are suspended and the roots misted with a nutrient solution, is another method for growing plants without soil.原句中acroponics意思是空气种植法，acro表示悬空，所以后面的解释是把植物怎么样，而且跟后面的mist并列，mist混合。混合与成长是不能并列的，grow错;同样C的铺开也不对;protect是完全不靠谱的。
Question 8 of 14
Question 9 of 14
题目解析：afford: 给予，提供。A是提供;B是防止;C是增加;D是一处。所以offer提供，给出是正确答案。对应原文：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.很多物种都生长在热带及亚热带地区，那儿的高浓度金属可以怎么样保护植物免遭吃植物的昆虫的捕食。从原文看，高浓度的金属应该是起到了正面的作用。B的prevent防止保护和D的remove去除保护肯定不对;increase增加保护是在原有的基础上增加，原文没说原来就有保护，所以increase不对。
Question 10 of 14
题目解析：这句话的主干部分并不长，such as后面开始时举例部分，可以先忽略不看。主干说：这个方案由种植species开始。由…开始对应C选项的first step，C正确。A中的before是没说的，原文一直在说这件事开始于什么什么，这件事之前干嘛没说;原文有个很难替换的词HAS，而这个词在B答案中没有，所以B错;C同义替换，正确;D把such as里面的例子变成了句子的主要部分，改变了结构，错。
Question 11 of 14
Question 12 of 14
Question 13 of 14
题目解析：三个过渡点，certain minerals，large quantities和代词others，有mineral的只有A和B两个选项;带入之后发现A是正确的，待插入句说有的矿物比别的矿物更容易沉积，而原文的第二句是对待插入句的一种解释，所以应该放在待插入句之后，所以A对B错。
Question 14 of 14
题目解析：从文章题目可以大致推测可能会有几种方向。物质对植物的重要性几个方面的描述/为什么特别重要解释/缺乏物质或过多的解决方法。 首段大致说的是物质对植物的重要性。 二段描述物质缺乏的症状。 三段补充介绍二段所说物质缺乏的研究方法：控制变量 四段说物质过多对植物的危害。 五段特定植物能用来吸收物质，实际说的是问题的可能解决方案。 末段说的是五段解决方案的具体操作，最新进展。 引出句概括的是首段内容。正确选项应概括后段内容。 A(some plants are)选项对应原文第五段和末段，正确。 B(though)选项对应原文第四段，正确。 C(when)选项对应原文第二段，正确。 D(because)选项中的因果关系原文没说，而且氯化钠也是个细节，不选。 E(some plants can)选项没说，不选。 F(mineral deficiency)选项是原文第三段末的一个细节，不选。