首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Insects which eat grain and other stored food can be partially controlled by cooling the grain. But the damage insects cause can
Insects which eat grain and other stored food can be partially controlled by cooling the grain. But the damage insects cause can
admin
2013-11-10
50
问题
Insects which eat grain and other stored food can be partially controlled by cooling the grain. But the damage insects cause can be further limited by making them even more susceptible to cold, says a Canadian researcher.
Insect pests die if they freeze, but many have the ability to become "supercool", remaining alive even when the temperature drops to - 10℃. However, Paul Fields of the Agriculture Canada Research Station in Winnipeg has discovered that the ability of these insects to supercool can be seriously affected by "ice-nucleating-active bacteria". When the bacteria are present, the insects freeze and die at a higher temperature than normal.
Ice-nucleating-active bacteria are found naturally on most plant leaves. They are also grown commercially for use in cloud seeding and in making artificial snow.
Fields added these bacteria to wheat which was stored at a temperature of - 10℃ and contained the rusty grain beetle. He found that when the bacteria accounted for only 10 parts per million of the grain, the beetles’ supercooling point rose from - 11.3℃ to - 7.1℃, so more died. At concentrations of 100 ppm or 1000 ppm, the bacteria increased the supercooling point to as high as -6.3℃, which resulted in more than 75 percent of the beetles dying.
Fields also applied the bacteria to two other species of grain beetle, Sitophilus granarius and Oryzaephilus surinamensis, keeping them at - 10℃. He found that more of these beetles also died. First, though, he gradually acclimatized some of the insects to cold, to simulate the increase in tolerance to cold which they normally develop as winter approaches. Fields found that the insects that had been acclimatized were less affected by cold than the beetles that had not been acclimatized, but that more of them still died at - 10℃.
Fields says that the technique of using ice-nucleating-active bacteria leaves no noxious chemical residues and poses little risk to the people who apply the treatment. It is also effective against insects which have become resistant to pesticides.
We learn from the passage that ______.
选项
A、the bacteria are only effective against three species of beetles
B、Fields’ technique is less effective in winter
C、Fields’ technique may kill nearly all the beetles at -10℃
D、Insects may develop resistance against the bacteria
答案
B
解析
根据第五段可知A、C两项不正确,B是正确答案,D没有提到。
转载请注明原文地址:https://kaotiyun.com/show/wlGK777K
0
专业英语四级
相关试题推荐
Howdidchildrenlearnintheearliesttimes?
Duringthewholeofadark,cloudydayneartheendoftheyearIhadbeen【C1】______myhorsealongcountryroadswithlittleli
Duringthewholeofadark,cloudydayneartheendoftheyearIhadbeen【C1】______myhorsealongcountryroadswithlittleli
WhyaresomanyChineseclothesstoredinEuropeancustomswarehouses?
Peopleinmodernsocietyliveunderalotofpressure,fromeducation,career,orfamily.Soitisimportantforthemtokeepa
Howmanypeopledidtheauthoritiesstartremovingfromthedangerousplacetoasaferone?
Little______aboutherownsafety,thoughsheherselfwasingreatdanger.(2009年考试真题)
It’ssupposedtobethebiggest,busiestdayoftheyearforonlineshopping—andastheamountwespendonlinegrowseachyear,
Isupposeheisquiteseriousaboutwhathesaidtoyou,______?
随机试题
简述政党的基本特征。
肥厚型心肌病心肌最明显肥厚的部位在
下列哪一项是葡萄胎特征性声像图表现
A.缺氧B.麻醉和抑制作用C.阻断神经介质D.抑制酶活力E.干扰细胞膜或细胞器生理功能
有关涂膜剂的不正确表述是
对现场自拌混凝土容易出现强度等级偏低,不符合设计要求的质量通病,项目部制定了下列防治措施,正确的有()。
150多年来,一些重大发明,如照明、通信、汽车灯技术,都是在世博会上面世后才逐渐转化为主流产业的。从文化生活角度看,这是因为()。
下列选项中,构成犯罪未遂的是()。
设f(x)在[a,b]上连续,在(a,b)内可导,且f(a)=f(b)=0,证明:存在ξ∈(a,b),使得f’(ξ)=2ξf(ξ).
以下关于VB的叙述中,错误的是()。
最新回复
(
0
)