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According to the famous song, American 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 rippling5 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 seedlings6 undergo a process called cold acclimation7. They begin to grow and poke8 through the soil as the temperature drops to around forty-eight degrees Fahrenheit9. 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 genes10 that help the plant tolerate freezing temperatures. Although scientists do not fully11 understand precisely12 how this process works, it is clear that carbon production and freezing tolerance13 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.
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1 spacious | |
adj.广阔的,宽敞的 | |
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2 amber | |
n.琥珀;琥珀色;adj.琥珀制的 | |
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3 lyrics | |
n.歌词 | |
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4 mid | |
adj.中央的,中间的 | |
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5 rippling | |
起涟漪的,潺潺流水般声音的 | |
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6 seedlings | |
n.刚出芽的幼苗( seedling的名词复数 ) | |
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7 acclimation | |
n.服水土,顺应,适应环境;服习;驯化 | |
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8 poke | |
n.刺,戳,袋;vt.拨开,刺,戳;vi.戳,刺,捅,搜索,伸出,行动散慢 | |
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9 Fahrenheit | |
n./adj.华氏温度;华氏温度计(的) | |
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10 genes | |
n.基因( gene的名词复数 ) | |
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11 fully | |
adv.完全地,全部地,彻底地;充分地 | |
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12 precisely | |
adv.恰好,正好,精确地,细致地 | |
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13 tolerance | |
n.宽容;容忍,忍受;耐药力;公差 | |
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