『新东方在线托福阅读』为托福考生准备了ETS托福TPO/Official 5 Passage 1阅读练习：The word “afford” in the passage is closest in meaning to真题题目及答案解析，TPO/Official 5 Passage 1阅读原文范文音频翻译

托福TPO/Official 5 Passage 1阅读原文The word “afford” in the passage is closest in meaning to题目答案及解析-新东方托福官方网校手机版

研究表明，植物需要某些矿物质才能正常生长和发育。

Research has shown that certain minerals are required by plants for normal growth and development.

土壤是这些矿物质的来源，这些矿物质会被来自土壤中的水吸收。

The soil is the source of these minerals, which are absorbed by the plant with the water from the soil.

即使是元素状态的气体氮气，也通常以硝酸根离子的形式从土壤中吸收。

Even nitrogen, which is a gas in its elemental state, is normally absorbed from the soil as nitrate ions.

众所周知，有些土壤缺乏微量营养素，因此无法维持大多数植物的生命。

Some soils are notoriously deficient in micro nutrients and are therefore unable to support most plant life.

例如，所谓的蛇纹石土壤缺乏钙，只有能够忍受少量这种矿物质的植物才能生存。

So-called serpentine soils, for example, are deficient in calcium, and only plants able to tolerate low levels of this mineral can survive.

在现代农业中，土壤的矿物质消耗是一个主要问题，因为收割庄稼会中断养分循环回土壤的这一过程。

In modern agriculture, mineral depletion of soils is a major concern, since harvesting crops interrupts the recycling of nutrients back to the soil.

矿物质缺乏症通常可以通过特定症状来检测，例如萎黄病（叶绿素丢失，导致黄色或白色的叶子组织形成），坏疽（孤立的死斑），花色苷（花青素）形成（叶子或茎有深红色素积累），发育不良和草本植物中木质组织的发育。

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.

氮和磷是土壤中最常缺的物质。

Soils are most commonly deficient in nitrogen and phosphorus.

缺氮植物表现出上述许多症状。

Nitrogen-deficient plants exhibit many of the symptoms just described.

叶片发育萎黄；茎短而纤细；以及发生在茎，叶柄和下部叶片表面的花青素变色现象。

Leaves develop chlorosis; stems are short and slender; and anthocyanin discoloration occurs on stems, petioles, and lower leaf surfaces.

缺磷植物常发育不良，叶片呈现出典型的深绿色，且常伴有花青素的积累。

Phosphorus-deficient plants are often stunted, with leaves turning a characteristic dark green, often with the accumulation of anthocyanin.

通常情况下，随着磷被转移到年轻的生长组织上，较老的叶子首先受到影响。

Typically, older leaves are affected first as the phosphorus is mobilized to young growing tissue.

缺铁的特征是幼叶的叶脉间发生黄化。

Iron deficiency is characterized by chlorosis between veins in young leaves.

关于养分缺乏的许多研究都是基于水培法种植植物，即在无土的液态养分溶液中进行的。

Much of the research on nutrient deficiencies is based on growing plants hydroponically, that is, in soilless liquid nutrient solutions.

这项技术使得研究人员能够创造出选择性地忽略某些营养成分的溶液，从而可以观察其对植物的影响。

This technique allows researchers to create solutions that selectively omit certain nutrients and then observe the resulting effects on the plants.

水培法已经有了超出基础研究范围的应用，因为它促进了冬季温室蔬菜的生长。

Hydroponics has applications beyond basic research, since it facilitates the growing of greenhouse vegetables during winter.

气培法是一种使植物悬浮并用营养液喷洒植物根部的技术，是另一种无土栽培方法。

Aeroponics, a technique in which plants are suspended and the roots misted with a nutrient solution, is another method for growing plants without soil.

尽管矿物质缺乏会限制植物的生长，但是某些矿物质的过量会产生毒性，也可能限制植物的生长。

While mineral deficiencies can limit the growth of plants, an overabundance of certain minerals can be toxic and can also limit growth.

盐碱地含有着高浓度的氯化钠和其他盐类，限制了植物的生长，因而研究持续集中于开发耐盐的农作物品种。

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.

研究集中在如铅、镉、汞和铝这样的重金属的毒性作用;然而，即使是作为基本元素的铜和锌，在高浓度下同样会产生毒性。

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.

尽管大多数植物不能在这种土壤中生存，但某些植物有能力忍受高浓度含量的这些矿物质。

Although most plants cannot survive in these soils, certain plants have the ability to tolerate high levels of these minerals.

科学家们早就得知某些被称为超蓄积植物的植物可以将矿物质的浓缩水平提高到正常水平的一百倍或更高。

Scientists have known for some time that certain plants, called hyperaccumulators, can concentrate minerals at levels a hundredfold or greater than normal.

一项对已知超蓄积植物的调查发现，其中75%的植物积聚了镍;钴、铜、锌、锰、铅和镉则是其他备选的矿物质。

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.

它们可能是草本植物、灌木或树木。

芥菜科，大麦科，豆类科和草科的许多成员都是顶级的超蓄积植物。

Many members of the mustard family, spurge family, legume family, and grass family are top hyperaccumulators.

热带和亚热带地区发现了众多这类植物，这些地区的高浓度金属积累可以为植物提供保护以抵御植食昆虫和微生物病原体。

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.

直到最近，研究人员才考虑使用这些植物来清理被达到毒性水平的重金属污染的土壤和废物处理场，这是一种称为植物修复的环保方法。

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.

此方案首先在目标地区种植超蓄积植物，例如在废弃的矿山或在被径流污染的灌溉池塘。

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.

有毒矿物质首先会被根吸收，然后又转移到茎和叶上。

Toxic minerals would first be absorbed by roots but later relocated to the stem and leaves.

收获的嫩芽会将有毒的化合物从燃烧或堆肥的地方清除出来，从而回收金属以做工业使用。

A harvest of the shoots would remove the toxic compounds off site to be burned or composted to recover the metal for industrial uses.

经过数年的耕种和收获，该地区的修复成本将大大低于修复污染土壤的标准做法，也就是挖掘和重新掩埋的费用。

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.

例如，在田间试验中，高山植物菥蓂从锌冶炼厂附近的土壤中去除了锌和镉，而原产于巴基斯坦和印度的印度芥菜则在污染土壤中有效地降低了50%的硒盐水平。

For example, 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.

According to paragraph 1, what is true of plants that can grow in serpentine soils?

The word “exhibit” in the passage is closest in meaning to

According to paragraph 2, which of the following symptoms occurs in phosphorus-deficient plants but not in plants deficient in nitrogen or iron?

According to paragraph 2, a symptom of iron deficiency is the presence in young leaves of

The word “facilitates” in the passage is closest in meaning to

According to paragraph 3, what is the advantage of hydroponics for research on nutrient deficiencies in plants?

The word “suspended” in the passage is closest in meaning to

Why does the author mention “herbs,” “shrubs,” and “trees ”?

The word “afford” in the passage is closest in meaning to

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.

It can be inferred from paragraph 6 that compared with standard practices for remediation of contaminated soils, phytoremediation

Why does the author mention “Indian mustard”?

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 would the sentence best fit? Click on a square  to add the sentence to the passage.

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 sentences 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.

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 example, 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.