普特聽力材料：揭秘雜草重生的秘密

　　我們經常很容易發(fā)現，雜草被人們鏟除了一段時間后，又會很快長出來。這是為什么呢?接下來，小編帶你走進這篇普特聽力材料，揭秘雜草重生的秘密。

　　Crabgrass is an ugly, obnoxious weed that is the scourge 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 nutrients. However, scientists have long wondered if crabgrass dominates your lawn’s real estate by using a technique called allelopathy. This literally means “others suffering,” and occurs when a plant harms another by emitting toxic 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 isolated three chemicals from crabgrass roots and nearby soil, and then added them to potted plants of wheat, maize, and soybeans. Sure enough, the plants treated with crabgrass toxins did not grow as well.

　　Chemical Warfare

　　Tests revealed that the compounds reduced the amount of carbon in the soil’s microbial biomass. This means crabgrass can actually change the makeup 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.

　　雜草丑陋而令人生厭。是整齊的草坪和崇尚完美主義園丁的禍害。除了難看之外，它還要為商業(yè)農場農作物收成大量受損承擔責任。

　　淘汰競爭

　　按照常理，這種雜草很難根除是因為它排擠周圍的植物使得它們沒有充足的生長空間和養(yǎng)料。然而，科學家們一直想知道，這種雜草是否通過使用一種名為植化相克的方法支配你家草坪的居住權。這個術語字面上的意思是"非我族類，連根清除"。當某種植物通過釋放有毒物質到環(huán)境中(通常通過土壤)來傷害其他植物時，這種現象就在發(fā)生。

　　來自南開大學，中國農業(yè)大學，和中國科學院的研究人員都發(fā)現這種雜草使用這個方法清除周圍的植物。

　　在實驗中，研究人員從這種雜草的.根部和其周圍土壤中隔絕出三種化學物質，然后將它們加入盆栽的小麥，玉米和大豆中。不出所料，受這種雜草毒素影響的植物都生長不佳。

　　化學戰(zhàn)爭

　　這些試驗揭示了該復合物降低了碳在土壤中微生物生物量中碳的數量。這意味著這種雜草確實能夠改變其周圍泥土中細菌的組成。因為植物依靠細菌來吸收諸如氮和有機化合物這樣的重要養(yǎng)分，邪惡的雜草使它的鄰居的生存極為艱難。

　　所以下次，當你向那一撮討厭的雜草噴除草劑時，要記住雜草自身會釋放一些除草劑。在你的眼皮子底下進行一場化學戰(zhàn)爭。

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