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
D.To explain how zinc contamination can be reduced
第1题
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
第2题
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.
Which of the sentences below best expresses the essential information in the highlighted sentence in paragraph 6? 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.
第3题
The word "afford" in the passage is closest in meaning to
A.offer
B.prevent
C.increase
D.remove
第4题
ncentrate 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.
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
第5题
The word "suspended" in the passage is closest in meaning to
A.grown
B.protected
C.spread out
D.hung
第6题
ficiencies 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.
第7题
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.
The word "facilitates" in the passage is closest in meaning to
A.slows down
B.affects
C.makes easier
D.focuses on
第8题
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
第9题
lants 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
第10题
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.
The word "exhibit" in the passage is closest in meaning to
A.fight off
B.show
C.cause
D.spread
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