问题 问答题 简答题

决定植物细胞脱分化、再分化的关键因素是什么?

答案

参考答案:

影响脱分化的一个重要因素是植物激素。当细胞分裂素与生长素共同使用时,能强烈促进愈伤组织的形成,而两者不同的浓度配比在再分化过程中,分别对诱导根或芽的产生起关键作用。当细胞分裂素与生长素浓度比高时,有利于芽的发生;浓度比低时,有利于根的发生。

单项选择题 案例分析题
单项选择题

Research on animal intelligence always makes us wonder just how smart humans are. (1) the fruit-fly experiments described by Carl Zimmer in the Science Times. Fruit flies who were taught to be smarter than the average fruit fly (2) to live shorter lives. This suggests that (3) bulbs burn longer, that there is a(n) (4) in not being too bright.

Intelligence, it (5) , is a high-priced option. It takes more upkeep, burns more fuel and is slow (6) the starting line because it depends on learning — a(n) (7) process — instead of instinct. Plenty of other species are able to learn, and one of the things they’ve apparently learned is when to (8) .

Is there an adaptive value to (9) intelligence That’s the question behind this new research. Instead of casting a wistful glance (10) at all the species we’ve left in the dust I.Q.-wise, it implicitly asks what the real (11) of our own intelligence might be. This is (12) the mind of every animal we’ve ever met.

Research on animal intelligence also makes us wonder what experiments animals would (13) on humans if they had the chance. Every cat with an owner, (14) , is running a small-scale study in operant conditioning. We believe that (15) animals ran the labs, they would test us to (16) the limits of our patience, our faithfulness, our memory for locations. They would try to decide what intelligence in humans is really (17) , not merely how much of it there is. (18) , they would hope to study a(n) (19) question: Are humans actually aware of the world they live in (20) the results are inconclusive.

12()

A.outside

B.on

C.by

D.across