英語聽力文摘種子休眠

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Seed Dormancy

種子休眠是，有生活力的種子由于內(nèi)在原因，在適宜的環(huán)境條件下仍不能萌發(fā)的現(xiàn)象。休眠是植物在長期系統(tǒng)發(fā)育過程中獲得的一種抵抗不良環(huán)境的適應(yīng)性。具有休眠特性的農(nóng)作物種子在高溫多雨地區(qū)可防止穗發(fā)芽;某些沙漠植物的種子可以休眠狀態(tài)度過干旱季節(jié)，以待合適的萌發(fā)條件。種子休眠的原因可歸為兩大類：第一類是胚本身的因素造成的，包括胚發(fā)育未完成;生理上未成熟;缺少必須的激素或存在抑制萌發(fā)的物質(zhì)。用低溫層積、變溫處理、干燥、激素處理等方法可解除休眠。第二類是種殼(種皮和果皮等)的限制造成的。包括種殼的機械阻礙、不透水性、不透氣性以及種殼中存在抑制萌發(fā)的物質(zhì)等原因。用物理、化學(xué)方法破壞種皮或去除種殼即可解除休眠。

Learn about seed dormancy on this Moment of Science.

A man named William James Beal started an experiment in 1879, which has become the longest-running(持續(xù)時間最長的) test of seed dormancy in soil.

Beal buried twenty bottles containing sand and seeds from twenty-one common plants. He buried the bottles eighteen inches underground, (1)uncorked(拔去塞子) to allow in oxygen, and upside down to prevent water from accumulating in the bottles and drowning the seeds. The experiment was designed to test how long these various seeds could survive under virtually natural conditions before they would lose their ability to produce a plant.

Seed dormancy is why some seeds wait for the correct season before they (2)germinate(發(fā)芽). They’re (3)programmed to(按程序做事) wait for conditions suitable to the plant’s survival. Seed dormancy is also why weeds are never-ending (4)nuisances(麻煩事，騷擾行為). Weed seeds can (5)lurk(潛伏) underground unseen, and then when you till(耕種) soil to make way for a flower bed, the seeds awaken and before you know it, your flower bed is (6)overrun(泛濫) with the pesky(討厭的，麻煩的) weeds.

Most of the seeds in Beal’s experiment were still viable(能養(yǎng)活的) after ten years, but as time passed, fewer and fewer of the seeds would germinate. The fifteenth of Beal’s twenty bottles was dug up in 2000, 120 years after it was buried, and two species were successfully germinated–moth mullein(蛾毛蕊花) and a mallow(錦葵) called cheeses. These are also the same two species that grew from the fourteenth bottle in 1980.

The plant that holds the record for the longest dormancy is a lotus(蓮花) that was sprouted in 1995 from a seed that radiocarbon(放射性碳素) dating estimated to be a whopping(巨大的) 1300 years old. Now that’s one stubborn seed.

注釋：

(1)uncork [,?n'k?:k]

vt. 泄漏;透露;發(fā)泄;拔去塞子

DO NOT uncork the champagne but it may be worth cracking open a beer.

開香檳慶祝也許為時尚早，不過開瓶啤酒痛飲一番還是值得的。

(2)germinate ['d??:mineit]

vt. 使發(fā)芽;使生長

vi. 發(fā)芽;生長

1..I don't know how the idea germinated in my mind.

我不知道這個想法在我的頭腦中是怎么產(chǎn)生的。

2.Seeds germinate in the spring.

種子在春天發(fā)芽。