我們經常很容易發現，雜草被人們剷除了一段時間後，又會很快長出來。這是爲什麼呢?接下來，小編帶你走進這篇普特聽力材料，揭祕雜草重生的祕密。
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.
雜草醜陋而令人生厭。是整齊的草坪和崇尚完美主義園丁的禍害。除了難看之外，它還要爲商業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爲它排擠周圍的`植物使得它們沒有充足的生長空間和養料。然而，科學家們一直想知道，這種雜草是否通過使用一種名爲植化相剋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境中(通常通過土壤)來傷害其他植物時，這種現象就在發生。
來自南開大學，中國農業大學，和中國科學院的研究人員都發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，然後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。
化學戰爭
這些試驗揭示了該複合物降低了碳在土壤中微生物生物量中碳的數量。這意味着這種雜草確實能夠改變其周圍泥土中細菌的組成。因爲植物依靠細菌來吸收諸如氮和有機化合物這樣的重要養分，邪惡的雜草使它的鄰居的生存極爲艱難。
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爭。
