托福阅读真题+题目+答案：The Evolution of Plant Roots

托福阅读真题+题目+答案：The Evolution of Plant Roots

Roots are essential to the development of large plants because they provide a means of anchoring and maintaining an upright position.⬛Most land plants are literally rooted to the spot.⬛Roots also play a key role in water and nutrient acquisition.⬛More significantly still, roots have a tremendous impact on the environment. ⬛They can break up rock, bind loose particles together, and prov idea conduit for the movement of water and dissolved minerals,all of which are essential to the development of soils.

1.In paragraph 1, which of the following is NOT mentioned as one of the ways in which roots

contribute to the development of soils?

O Holding loose soil particles together

O Releasing minerals into the Soil

O Splitting apart rock

O Helping transport water in the soil

In piecing together a fossil plant to form a conceptual whole, it is usually the rooting system that remains the final piece in the puzzle. It is often the case that roots are poorly studied or completely unknown.Although the fossil record of roots is therefore less complete than that of other plant organ systems, it is possible to discern some general trends.The earliest land plants, like modern mosses and liverworts,did not have well-developed root systems.These plants simply bore absorbing hairlike cells on stems and leaves that grew flat along the ground.From their fossils,some very early plants are known to have borne branches that appear to be specially modified for rooting. In other cases, roots were able to form from dormant buds on aerial stems.Fungi are also known to have played a key role in these early rooting systems, as they do in modern plants.Fungal symbionts—fungi that live in mutually beneficial relationships with another organism-have been recorded in the petrified plants of the 400million-year-old Rhynie Chert fossil site in Scotland, demonstrating a link with mycorrhizal fungi that goes back to the dawn of the land flora.These tiny, shallow rooting systems were adequate for small plants (30-50 centimeters tall), but larger organisms required something more substantial.

2.The word "discern" in the passage is closest in meaning to

O imagine

O notice

O describe

O propose

3.why does the author mention the existence of fungal symbionts in"the petrified plants of the 400million-year-old Rhynie Chert fossil site in Scotland”?

O To suggest that mycorrhizal fungi had been present in early plants before the fungi developed a special association with rooting systems

O To show how early in the history of land plants fungi had begun to play an important role in rooting systems

O To help explain why shallow rooting systems were adequate for very early plants

O To make the point that in spite of many differences, early and modern plants have important similarities

By the Late Devonian and Early Carboniferous eras (385 to 300 million years ago), an enormous variety of rooting structures had evolved.The evolution of large erect plants, and in particular trees,placed increasing demands upon the anchoring and supply functions of roots.These problems were solved mainly through the development of more extensive underground systems.The evolution of the cambium, the layer of living cells between wood and bark,enabled continuous perennial growth and long-term survival of roots in soils.

4.All of the following are mentioned in paragraph 3 as having evolved by the Late Devonian and Early Carboniferous eras EXCEPT

O a large number of different root systems

O trees and other tall plants

O a layer of cells that enabled continuous plant growth

O plants that grew mainly underground

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