题干

为了研究从植物中提取的可可碱是否可以作为除草剂,某科研小组开展了可可碱对鬼针草根尖细胞有丝分裂和种子萌发影响的实验探究,结果如下表所示。请回答。

可可碱浓度

(mmol•L-1)

根尖细胞有丝分裂

种子发芽率(%)


有丝分裂指数(%)

分裂期细胞占比(%)


前期和中期

后期和末期


0

3.73

3.04

0.69

81.5


0.1

2.90

2.16

0.74

68.1


0.5

2.10

1.72

0.38

18.6


1.0

1.96

1.72

0.24

2.3


注:有丝分裂指数=分裂期细胞数/观察细胞的总数×100%。

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同类题1

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    汉字是书法的载体。汉字起源于物象,“近取诸身,远取诸物”,象形会意形声而成字,日月山水,花鸟鱼虫,莫不如此。汉字发展的独特路径深刻地影响了中国文化与中国历史的面貌。

    汉字是前人千百年的书写实践而成,体现了汉字的结构美学与书写规律:横平竖直,点画呼应,上下包容,左右礼让,以形成中正平和之体。就像人要端庄、树要挺拔一样,每个字都是独立不倚的自我平衡体。谐调性、整体性、稳定性,是汉字的美学原则。谐调性是核心,只有谐调才能实现整体性与稳定性。所谓书法,就是书写汉字的法规与法度。书法成为艺术,恰恰是在汉字的“书写”过程中逐渐自觉形成的。

    书法作为一种艺术,不仅传达着个人的才情气质,也承载着时代的精神气象。被后人广泛而长期推崇的书法家王羲之,他的行书,形质坚毅,洒脱飘逸,骨气与逸气并生,法度与风 度共存。这是王羲之个人的学养气质与书法造诣所致,更与那个时代相关。因为那是一个精神解放、人格独立、文化自觉的时代。魏晋时期,士人倾心寄情山水,追求不拘礼节的闲适与放达,寻求精神人格的自在真实,并形成以人为本的审美自觉——从人的音容笑貌、筋骨气色、举止风姿看人的禀赋气质,探求人的形神之美,以至于一系列艺术美学概念由此而生,诸如形神、气韵、风骨等等。汉字结构与书法艺术不可避免地受到了这种时代风气的影响。

    唐代的社会气象与精神气度推动着唐人绕过王羲之而另辟蹊径,开创书法的新天地与新境界。唐人在书法上的贡献是以楷书为代表。颜真卿的楷书,磅礴伟岸,每一个字犹如一尊尊佛,雍容宽博,自信从容。如果说初唐时期的楷书承续了王羲之以来的隽永书风,那么,经过盛唐,南北融合,国势强盛,时代气象投射到文化之中,苍劲与粗犷之气化入楷书,出现了颜真卿、柳公权等书家,笔画中潜在着一种无形的力量。千百年来,欧体字与颜体字,分别代表了遒劲与雄放的高度,成为楷书的标本,后人难以企及。

    宋代承续了唐代文化,但难以逾越唐人。在楷书上,唐人几乎穷尽了法度与风格,宋人一时也找不到拓荒之处,于是在意态上自由发挥。苏轼、黄庭坚等人不刻意讲究点画的平直均衡,而以自己深厚的学养与才气入书,强调笔势的提按顿挫之意,形成夸张变形的欹侧姿态,这就是人们所说的宋人“尚意”。尚意,就是注重个人意趣,显露个性,出新意于法度之外,但 毕竟没有在法度上再创新格。

    元明清时期的书法有法度和功力,技法娴熟,但就是缺少一种力量、缺少一种卓尔不群的精神气象。书法更多的成为一种实用技法,而很少成为个人情感与精神的抒发。加之明清不清明,大兴文字狱,思想禁锢,精神压抑,书法中再难见到率性而为的天真烂漫。精神被桎梏 的时代,诗文和书法仅仅剩下了形式,唯美而干瘪,形体虽在,生气难寻。

    书法是心迹,也是时代精神气象的载体。如果说书法是汉字的舞姿,那么,这舞姿摇曳的是书法家的心性,也是时代的精神气象。

(《人民日报》2014 年07月31日)

同类题4

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   Have you ever had trouble sleeping in a new place?
   Lots of people do. And now researchers from Brown University in Rhode Island think they know why. They found that one-half of the brain "remains more awake" than the other half when people are trying to sleep in a new place.
   The sleep findings were reported in Current Biology by Brown University. In their report, the researchers said many people report they have a harder time sleeping the first night  at a hotel or other places outside their home. They call it "first-night influence". "In Japan they say, 'If you change your bed, you can't sleep,'" said Yuka Sasaki, one of the report's writers. "You don't sleep very well in a new place. We all know about it."
   The researchers measured brain waves (测量脑波) for 35 volunteers over two nights in a laboratory. The two nights were a week apart (间隔). They found during the first night the left half of the brain was more active than the right half. This was during the first deep-sleep period, the researchers said. 
   Sasaki said a lot of questions remain.
   Researchers did not keep measuring brain waves all night long. So, they don't know if the left half keeps "watch" all night, or whether it "works in shifts (轮换) with the right half later in the night". They also do not know why the brain activity, at least during the first period of deep sleep, is always on the left half.
   For some, this research may be calming. It is good to know that our brain is "looking out for us" in a new place. But it may not help with sleep. That brain activity, at least according to this new research, makes it harder to get the sleep people need to wake up well rested in the morning.