英语听力文摘 English Digest 717 杂草为何容易重生？

Why Crabgrass Always Wins at Monopoly

Crabgrass is an ugly, obnoxious¹ weed that is the scourge² of the perfect lawn and its perfectionist gardener. Along with being an eyesore, it’s also responsible for a substantial amount of crop loss on commercial farms.

Weeding Out Competition

Common wisdom says that crabgrass is hard to get rid of because it crowds out the plants around it, and does not allow them to get enough space and nutrients³. However, scientists have long wondered if crabgrass dominates your lawn’s real estate by using a technique called allelopathy. This literally⁴ means “others suffering,” and occurs when a plant harms another by emitting toxic⁵ substances into the environment, usually through the soil.

Researchers from Nankai University, China Agricultural University, and the Chinese Academy of Sciences all found that crabgrass uses this method of “weeding out” neighboring plants.

In their experiment, researchers isolated⁶ three chemicals from crabgrass roots and nearby soil, and then added them to potted plants of wheat, maize⁷, and soybeans. Sure enough, the plants treated with crabgrass toxins⁸ did not grow as well.

Chemical Warfare⁹

Tests revealed that the compounds reduced the amount of carbon in the soil’s microbial biomass. This means crabgrass can actually change the makeup¹⁰ of the bacteria in the dirt around it. Since plants rely on bacteria in order to absorb key nutrients such as nitrogen and organic compounds, the vicious weed makes life extremely hard on its surrounding neighbors.

So the next time you squirt Round?Up on that pesky patch of crabgrass, remember that the weed is emitting a little herbicide of its own. It’s chemical warfare, right under your nose.

1 obnoxious   

adj.极恼人的，讨人厌的，可憎的

参考例句：

• These fires produce really obnoxious fumes and smoke.这些火炉冒出来的烟气确实很难闻。
• He is the most obnoxious man I know.他是我认识的最可憎的人。

2 scourge   

n.灾难，祸害；v.蹂躏

参考例句：

• Smallpox was once the scourge of the world.天花曾是世界的大患。
• The new boss was the scourge of the inefficient.新老板来了以后，不称职的人就遭殃了。

3 nutrients   

n.（食品或化学品）营养物，营养品( nutrient的名词复数 )

参考例句：

• a lack of essential nutrients 基本营养的缺乏
• Nutrients are absorbed into the bloodstream. 营养素被吸收进血液。 来自《简明英汉词典》

4 literally   

adv.照字面意义，逐字地；确实

参考例句：

• He translated the passage literally.他逐字逐句地翻译这段文字。
• Sometimes she would not sit down till she was literally faint.有时候，她不走到真正要昏厥了，决不肯坐下来。

5 toxic   

adj.有毒的，因中毒引起的

参考例句：

• The factory had accidentally released a quantity of toxic waste into the sea.这家工厂意外泄漏大量有毒废物到海中。
• There is a risk that toxic chemicals might be blasted into the atmosphere.爆炸后有毒化学物质可能会进入大气层。

6 isolated   

adj.与世隔绝的

参考例句：

• His bad behaviour was just an isolated incident. 他的不良行为只是个别事件。
• Patients with the disease should be isolated. 这种病的患者应予以隔离。

7 maize   

n.玉米

参考例句：

• There's a field planted with maize behind the house.房子后面有一块玉米地。
• We can grow sorghum or maize on this plot.这块地可以种高粱或玉米。

8 toxins   

n.毒素( toxin的名词复数 )

参考例句：

• The seas have been used as a receptacle for a range of industrial toxins. 海洋成了各种有毒工业废料的大容器。
• Most toxins are naturally excreted from the body. 大部分毒素被自然排出体外。 来自《简明英汉词典》

9 warfare   

n.战争(状态)；斗争；冲突

参考例句：

• He addressed the audience on the subject of atomic warfare.他向听众演讲有关原子战争的问题。
• Their struggle consists mainly in peasant guerrilla warfare.他们的斗争主要是农民游击战。

10 makeup   

n.组织；性格；化装品

参考例句：

• Those who failed the exam take a makeup exam.这次考试不及格的人必须参加补考。
• Do you think her beauty could makeup for her stupidity?你认为她的美丽能弥补她的愚蠢吗？