Germination and Growth of a seed托福聽力原文翻譯及問題答案

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Germination and Growth of a seed托福聽力原文翻譯及問題答案

一、Germination and Growth of a seed托福聽力原文：

Our study of the life cycle of a plant usually starts with the germination of a seed.The seed contains the hereditary information the plant needs to grow.It also contains enough food to nourish itself during germination.

Heredity—the genes inherited from the parent plant—decides several things about the life of the plant.Heredity determines what the plant will look like,how it will grow,and what kind of seeds it will bear.Inside the seed is all the genetic information the plant needs to grow to maturity.An individual plant’s survival depends partly on its hereditary characteristics.But a plant depends on more than just heredity.It needs the outside world to supply its daily needs:sunlight,carbon dioxide,nutrients,and water.

Some seeds germinate as soon as they’re in a suitable environment.Other seeds remain dormant and won’t germinate until a specific environmental cue causes them to“wake up”and come out of dormancy.Seeds of desert plants germinate only after a heavy rainfall.If they germinated after a slight rain,the soil might soon be too dry to support the seedlings.Seed dormancy increases the chances that germination will take place at a time and place that are best for the seedling.

Germination begins when water penetrates the seed’s outer coating and reaches inside to the live embryo.Water is a basic requirement,and no seed will germinate unless it absorbs water.This is because the embryo inside the seed is dehydrated,and cells need water for active metabolism.Water is the substance in which most of the chemical reactions of the plant take place.

For a seed to sprout and grow,it needs a great deal of energy.Seeds get this energy by converting the energy of their stored fuel molecules,and this requires oxygen.Germination also requires a certain combination of temperature and light,which,in North America,is triggered by the start of spring.Some seeds respond early in the season,others much later.Each plant species has an ideal temperature at which the largest number of seeds will germinate.

When the embryo takes in water,it often swells to several times its original size.It gets this first burst of energy by tapping its own food stores.Eventually,the seed expands enough to rupture its coating and burst through the seed case.

The first organ to emerge from the germinating seed is the embryonic root.The root pushes outward into the soil and anchors the seedling.Now the seedling begins to gather up water and nutrients through thousands of tiny hair-like roots.After a certain period,the seedling sprouts upward.The tip of the shoot has to break through the soil surface.Light is the environmental cue that tells the seedling when it’s broken ground.Only when the seedling senses light will it straighten up and begin to grow taller.As it straightens up and grows,it unfolds its solar collectors,its first leaves.Once the seedling has its main leaves,it doesn’t need its embryonic food stoics anymore because now it draws most of its growth energy directly from the sun.

The germination of a seed is a critical stage in the plant’s life cycle.The tough seed becomes a fragile seedling,and only a small fraction of seedlings survive long enough to become parent plants.Because the chances of a seedling’s survival arc so low,plants make up for this by producing enormous numbers of seeds.

二、Germination and Growth of a seed托福聽力中文翻譯：

我們對植物生命周期的研究通常從種子發(fā)芽開始。種子含有植物生長所需的遺傳信息。它還含有足夠的食物，可以在發(fā)芽過程中自我滋養(yǎng)。

遺傳——從親本植物遺傳的基因——決定了植物生命的幾個方面。遺傳決定了植物會是什么樣子，它會如何生長，以及它會結(jié)出什么樣的種子。種子內(nèi)部是植物生長成熟所需的所有遺傳信息。植物個體的生存在一定程度上取決于其遺傳特征。但是一種植物不僅僅依賴于遺傳。它需要外界來滿足它的日常需求：陽光、二氧化碳、營養(yǎng)物質(zhì)和水。

有些種子一進入合適的環(huán)境就會發(fā)芽。其他種子仍處于休眠狀態(tài)，直到特定的環(huán)境提示使它們“醒來”并脫離休眠，才會發(fā)芽。沙漠植物的種子只有在強降雨后才會發(fā)芽。如果它們在微雨后發(fā)芽，土壤可能很快就會過于干燥，無法支撐幼苗。種子休眠增加了在對幼苗最有利的時間和地點發(fā)芽的機會。

當水滲透到種子的外殼并到達活胚的內(nèi)部時，發(fā)芽就開始了。水分是一種基本需求，除非種子吸收水分，否則它不會發(fā)芽。這是因為種子中的胚胎脫水，細胞需要水來進行活躍的新陳代謝。水是植物大多數(shù)化學反應(yīng)發(fā)生的物質(zhì)。

一顆種子要發(fā)芽和生長，需要大量的能量。種子通過轉(zhuǎn)換其儲存的燃料分子的能量來獲得這種能量，這需要氧氣。發(fā)芽還需要一定的溫度和光照組合，在北美，這是由春天的開始引發(fā)的。一些種子在季節(jié)早期就有反應(yīng)，另一些則晚得多。每種植物都有一個理想的溫度，在這個溫度下，最多的種子會發(fā)芽。

當胚胎吸收水分時，它通常會膨脹到原來大小的幾倍。它通過挖掘自己的食物庫來獲得第一次能量爆發(fā)。最終，種子膨脹到足以使其涂層破裂并穿過種子外殼。

發(fā)芽種子中出現(xiàn)的第一個器官是胚胎根。根部向外推入土壤并固定住幼苗?，F(xiàn)在，幼苗開始通過數(shù)千個毛發(fā)狀的細根收集水分和營養(yǎng)。經(jīng)過一段時間，幼苗向上發(fā)芽。芽尖必須穿透土壤表面。光是告訴幼苗何時破土的環(huán)境信號。只有當幼苗感覺到光線時，它才會挺直身子，開始長高。當它變直并生長時，它展開了它的太陽能收集器，這是它的第一片葉子。一旦幼苗長出了主葉，它就不再需要它的胚胎食物了，因為現(xiàn)在它的大部分生長能量都直接來自太陽。

種子的發(fā)芽是植物生命周期中的一個關(guān)鍵階段。堅韌的種子變成了脆弱的幼苗，只有一小部分幼苗存活足夠長的時間成為親本植物。由于幼苗存活的幾率很低，植物通過生產(chǎn)大量種子來彌補這一點。

三、Germination and Growth of a seed托福聽力問題：

Q1:1.What aspect of seeds does the professor mainly discuss?

A.Hereditary changes in seeds

B.Ways that seeds are dispersed

C.Genetic engineering of seeds

D.How seeds germinate and grow

Q2:2.What role does heredity play in the life of a plant?

A.It provides the information the plant needs to grow.

B.It helps nutrients move up from the soil into the plant.

C.It causes the seed to swell and burst out of its case.

D.It supplies the energy required to manufacture food.

Q3:3.Why does the professor say this:

A.To point out the diversity of plant life

B.To give an example of an environmental cue

C.To compare different ecosystems where plants live

D.To explain why few plants survive in the desert

Q4:4.What environmental factors are required for a seed to germinate?

Click on two answers.

A.Heredity

B.Water

C.Organic fertilizer

D.The proper temperature

Q5:5.How does a seed obtain the energy it needs for germination?

A.It takes in nutrients through capillaries in its roots.

B.It depends on the chemical energy from fertilizer.

C.It converts the energy of food stored within itself.

D.It uses solar energy collected through its leaves.

四、Germination and Growth of a seed托福聽力答案：

A1:正確答案：D

A2:正確答案：A

A3:正確答案：B

A4:正確答案：BD

A5:正確答案：C

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