英语听力文摘 English Digest 439、冬小麦

Winter Wheat

According to the famous song, America is beautiful for its spacious¹ skies, purple mountains, and amber² waves of grain. If you were to make a music video based on these lyrics³ you’d probably want mid⁴ to late summer images of fruit-laden trees and fields of rippling wheat under sunny blue skies.

But where the amber waves of grain are concerned, the image might be slightly misleading. While at least some wheat in the United States and Canada is planted in the spring and harvested in the summer, much is planted in the late fall and harvested in the spring.

Winter wheat manages to survive freezing temperatures and being buried under piles of snow. How do these plants pull it off?
After being planted in the mid to late fall, winter wheat seedlings⁵ undergo a process called cold acclimation. They begin to grow and poke⁶ through the soil as the temperature drops to around forty-eight degrees Fahrenheit⁷.

As the plant’s leaves absorb light the seedlings produce large amounts of carbon and store it in the crown, the part of the plant where root and shoot meet underground.

At the same time, the absorption of light combined with low temperatures triggers the expression of certain genes⁸ that help the plant tolerate freezing temperatures.

Although scientists do not fully⁹ understand precisely¹⁰ how this process works, it is clear that carbon production and freezing tolerance¹¹ are necessary for the plant’s survival.

When the snow melts and temperatures rise in the spring, the plant has plenty of stored energy for steady growth. By mid spring, many North American wheat fields are beautiful with waves of grain ready for harvest.

由那首著名的歌得知，美国因它广阔的天空，紫色的山峦，还有琥珀色的谷浪而美丽。如果你打算取材于这些歌词作曲，那你也许想要夏末载满果实的树和晴朗蓝天下翻滚的麦浪的图像吧。

但是有谷浪的地方，那样的形象也许稍令人误解吧。虽然美国和加拿大或多或少有些小麦是在春天播种，夏天收割，但大部分是晚秋播种，第二年春天收割的。
冬小麦设法在结冰的温度下生存，还要埋于厚厚的大雪下。这些作物是怎样成功生存的呢？

在仲秋或晚秋播种后，冬小麦种子经历了被称为冷驯化的过程。它们在气温降到48华氏温度后开始冲破土壤生长。当小麦叶吸收阳光后，种子产出大量的碳并储存在植物冠中，这是根和芽在地底下交汇的地方。

同时，吸收的光和低温结合促使某种基因的产生，以帮助作物忍耐低温。

尽管科学家们并未完全准确弄明白这个过程是怎样进行的，但是生产碳和忍受低温对作物的生长很必要，这一点是显而易见的。

春天雪融化，气温也升高了，这时冬小麦已经存储了大量供稳定生长的能量了。到仲春的时候，许多北美小麦地因有大片待收割的小麦浪而美丽无比。

 

1 spacious   

adj.广阔的，宽敞的

参考例句：

• Our yard is spacious enough for a swimming pool.我们的院子很宽敞，足够建一座游泳池。
• The room is bright and spacious.这房间很豁亮。

2 amber   

n.琥珀；琥珀色；adj.琥珀制的

参考例句：

• Would you like an amber necklace for your birthday?你过生日想要一条琥珀项链吗？
• This is a piece of little amber stones.这是一块小小的琥珀化石。

3 lyrics   

n.歌词

参考例句：

• music and lyrics by Rodgers and Hart 由罗杰斯和哈特作词作曲
• The book contains lyrics and guitar tablatures for over 100 songs. 这本书有100多首歌的歌词和吉他奏法谱。

4 mid   

adj.中央的，中间的

参考例句：

• Our mid-term exam is pending.我们就要期中考试了。
• He switched over to teaching in mid-career.他在而立之年转入教学工作。

5 seedlings   

n.刚出芽的幼苗( seedling的名词复数 )

参考例句：

• Ninety-five per cent of the new seedlings have survived. 新栽的树苗95%都已成活。 来自《现代汉英综合大词典》
• In such wet weather we must prevent the seedlings from rotting. 这样的阴雨天要防止烂秧。 来自《现代汉英综合大词典》

6 poke   

n.刺，戳，袋；vt.拨开，刺，戳；vi.戳，刺，捅，搜索，伸出，行动散慢

参考例句：

• We never thought she would poke her nose into this.想不到她会插上一手。
• Don't poke fun at me.别拿我凑趣儿。

7 Fahrenheit   

n./adj.华氏温度；华氏温度计(的)

参考例句：

• He was asked for the boiling point of water in Fahrenheit.他被问到水的沸点是华氏多少度。
• The thermometer reads 80 degrees Fahrenheit.寒暑表指出华氏80度。

8 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

9 fully   

adv.完全地，全部地，彻底地；充分地

参考例句：

• The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气，然后全部呼出。
• They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。

10 precisely   

adv.恰好，正好，精确地，细致地

参考例句：

• It's precisely that sort of slick sales-talk that I mistrust.我不相信的正是那种油腔滑调的推销宣传。
• The man adjusted very precisely.那个人调得很准。

11 tolerance   

n.宽容；容忍，忍受；耐药力；公差

参考例句：

• Tolerance is one of his strengths.宽容是他的一个优点。
• Human beings have limited tolerance of noise.人类对噪音的忍耐力有限。