Germination and Growth of a seed托福听力原文翻译及问题答案

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Germination and Growth of a seed托福听力原文翻译及问题答案

一、Germination and Growth of a seed托福听力原文：

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托福听力中文翻译：

我们对植物生命周期的研究通常从种子发芽开始。种子含有植物生长所需的遗传信息。它还含有足够的食物，可以在发芽过程中自我滋养。

遗传——从亲本植物遗传的基因——决定了植物生命的几个方面。遗传决定了植物会是什么样子，它会如何生长，以及它会结出什么样的种子。种子内部是植物生长成熟所需的所有遗传信息。植物个体的生存在一定程度上取决于其遗传特征。但是一种植物不仅仅依赖于遗传。它需要外界来满足它的日常需求：阳光、二氧化碳、营养物质和水。

有些种子一进入合适的环境就会发芽。其他种子仍处于休眠状态，直到特定的环境提示使它们“醒来”并脱离休眠，才会发芽。沙漠植物的种子只有在强降雨后才会发芽。如果它们在微雨后发芽，土壤可能很快就会过于干燥，无法支撑幼苗。种子休眠增加了在对幼苗最有利的时间和地点发芽的机会。

当水渗透到种子的外壳并到达活胚的内部时，发芽就开始了。水分是一种基本需求，除非种子吸收水分，否则它不会发芽。这是因为种子中的胚胎脱水，细胞需要水来进行活跃的新陈代谢。水是植物大多数化学反应发生的物质。

一颗种子要发芽和生长，需要大量的能量。种子通过转换其储存的燃料分子的能量来获得这种能量，这需要氧气。发芽还需要一定的温度和光照组合，在北美，这是由春天的开始引发的。一些种子在季节早期就有反应，另一些则晚得多。每种植物都有一个理想的温度，在这个温度下，最多的种子会发芽。

当胚胎吸收水分时，它通常会膨胀到原来大小的几倍。它通过挖掘自己的食物库来获得第一次能量爆发。最终，种子膨胀到足以使其涂层破裂并穿过种子外壳。

发芽种子中出现的第一个器官是胚胎根。根部向外推入土壤并固定住幼苗。现在，幼苗开始通过数千个毛发状的细根收集水分和营养。经过一段时间，幼苗向上发芽。芽尖必须穿透土壤表面。光是告诉幼苗何时破土的环境信号。只有当幼苗感觉到光线时，它才会挺直身子，开始长高。当它变直并生长时，它展开了它的太阳能收集器，这是它的第一片叶子。一旦幼苗长出了主叶，它就不再需要它的胚胎食物了，因为现在它的大部分生长能量都直接来自太阳。

种子的发芽是植物生命周期中的一个关键阶段。坚韧的种子变成了脆弱的幼苗，只有一小部分幼苗存活足够长的时间成为亲本植物。由于幼苗存活的几率很低，植物通过生产大量种子来弥补这一点。

三、Germination and Growth of a seed托福听力问题：

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托福听力答案：

A1:正确答案：D

A2:正确答案：A

A3:正确答案：B

A4:正确答案：BD

A5:正确答案：C