双语阅读:动物荷尔蒙大家都不陌生,但你知道植物也有荷尔蒙吗?

了解植物荷尔蒙

翻译:涂博士(微信号:jefftu95)

荷尔蒙就像一个无所不能的信使!

荷尔蒙的工作能力非常强。我们可以将荷尔蒙想象为在体内某个位置产生的化学信使,它们可以将信息传递到体内完全不同的位置。就像辣酱一样,虽然只要一点点辣酱,可产生的效果可以非常大。荷尔蒙的浓度通常都非常低,但荷尔蒙作用的结果大家都知道有多厉害吧!我们都知道荷尔蒙会导致人的身体发生很多变化(嗯,比如说青春期),但是你知道植物也有荷尔蒙吗?植物不会和人一样有诸如长体毛,长青春痘和声音变化等有趣经历,但下面我要告诉你的是荷尔蒙对植物生长和发育也有惊人的作用!

五大兄弟

我们将介绍五种主要的植物荷尔蒙:生长素,赤霉素,细胞分裂素,乙烯和脱落酸。这些荷尔蒙可以共同或独立地影响植物的生长。

生长素

你已经见过了生长素的作用。嗯,你虽然没有用肉眼看到过实际的生长素分子本身,但是你已经看到了它对在窗户附近生长的植物有什么影响。您是否想过植物为什么会向着阳光弯曲?让我告诉你,这就与植物茎中的生长素有关。达尔文和他的儿子也曾对此感到好奇(发表于:植物的力量与运动),但当时他们并不知道到底是什么导致植物向着光线弯曲。生长素本身直到1920年代末才被发现,它是人们要研究的5种主要植物荷尔蒙中的第一种。生长素担负有很多任务,但最重要的任务是刺激生长,如果植物本身不能自然地产生生长素,它将会死亡。因此,你可以看到生长素非常重要。生长素的技术别名是吲哚-3-乙酸或IAA(以防万一你看到的文字是“ IAA” –你将明白其意思与“ Auxin”相同)。

赤霉素

赤霉素在植物中引起的作用与生长素类似,但它是一种非常不同的荷尔蒙。赤霉素最初是在日本发现的。一种称为赤霉菌的真菌感染了水稻,导致它们长得过高而倒伏。这些感染性真菌产生的化学物质刺激了水稻的生长。在分离出该化学物质后,人们以真菌的名字来命名这化学物质,这就是赤霉素。后来发现,植物会自然地产生各式各样的赤霉素!

细胞分裂素

谁会想到鱼竟然会在植物荷尔蒙的发现中发挥作用?老迈的鲱鱼精子DNA可以促进细胞分裂,引起这个效果的分子称为激动素。不久之后,人们在植物中也发现了一种和激动素具有相同的生物学作用的物质。当这种物质与生长素一起培养时,它会刺激植物细胞分裂。该物质被称为细胞分裂素,它参与了细胞分裂和植物新器官的制造,例如根或芽。细胞分裂素产生于根尖的分生组织(根的顶端),并随着水流沿茎穿过木质部向上移动。细胞分裂素的移动不需要自身的能量,是完全被动的!

细胞分裂素就像是植物中的年轻的源泉。它们会延缓衰老即导致植物死亡的自然衰老过程。在细胞生命周期中,细胞分裂素促进了从G2期到M期的运动。换句话说,它们鼓励细胞分裂!

乙烯

你是否曾经注意到,如果您将熟透的棕色香蕉放在一堆绿色香蕉旁边,未成熟的香蕉会很快地成熟并变黄?这究竟是怎么发生的呢?我来告诉你吧,棕色香蕉与绿色香蕉会通过一种叫做乙烯的荷尔蒙进行通讯。乙烯是一种植物荷尔蒙,会影响植物的成熟和腐烂。它是一种特别有趣的植物荷尔蒙,因为它以气体形式存在。没有其他植物荷尔蒙是气体!乙烯几乎可以在植物的任何部分中产生,并且可以在植物的组织内,植物外部扩散,并通过空气传播,从而影响完全不同的植物,够酷的吧!

脱落酸

当我们的身体需要水时,我们会感到口渴。 “口渴信号”表示我们脱水了,我们需要喝水。当植物需要水时,例如在干旱期间,它没有太多选择,在雨中跳舞是想都不用想的。植物会产生一种称为脱落酸的化学信使,以提醒植物的其余部分现在水分紧缺。脱落酸是在干旱的叶片,干旱的根和发育中的种子中产生的,它可以在木质部或韧皮部的植物茎中上下移动,从而发出警报。

上面简要概述了五种主要的植物荷尔蒙:生长素,赤霉素,细胞分裂素,乙烯和脱落酸。请记住,荷尔蒙是小小的但又非常厉害的化学信使,但如果它们徘徊不动并在组织中堆积在一起,它们将失去效力。因此,它们会随着时间的流逝而被分解和更换掉。

在开始阅读英文原文之前,请先复习下列核心词汇​:

hormone - n. 荷尔蒙,激素
mighty - adj. 强壮的
messenger - n. 信使
get things done - 把事情完成,如果说某人能够get things done,就是夸他干活靠谱,总能完成交给他的任务
chemical - adj. 化学的
deliver - v. 传递
message - n. 信息
body - n. 身体
hot sauce - 辣酱
conceentration - n. 浓度
boy - n. 男孩,也经常用作感叹词,本文中的boy是感叹词
puberty - n. 青春期
influence - v. 影响
auxin - 生长素
gibberellin - 赤霉素
cytokinin - 细胞分裂素
ethylene - 乙烯
abscisic acid - 脱落酸
thirsty - adj. 渴
signal - n. 信号
dehydrate - v. 脱水
tissue - n. 组织
stimulate - v. 刺激

在复习了以上词汇后,请将下面的英文原文一口气读完,不要在中途停下来去查那些不认识的单词。有了上面的核心单词打底,你完全可以将整篇文章读完并且理解里面的大致意思。记住,你只要做到大致明白就可以了。

阅读能力和阅读量成正比,要提高阅读量,必须是大量的泛读,如果要对每个不懂的单词都去查字典,那么就不可能通过大量的泛读来提高你的阅读量。

如果你对某篇泛读文章特别喜欢,可以在泛读一遍以后再慢慢地精读。如果在精读的过程中对某些句子不是太明白需要讲解,或者你希望以后多看到哪方面的双语阅读,欢迎联系涂博士(微信号:jefftu95)。

Understanding Plant Hormones

Written by Rob Nelson

Hormones – Mighty Messengers!

Hormones get things done. Think of them as chemical messengers that are made in one place in the body and deliver their message in a totally different place in the body. And just like hot sauce, a little goes a long way. Hormones are usually found in very small concentrations, but boy to they pack a punch! We know hormones cause a lot of changes in humans (ah, puberty), but did you know that plants have hormones, too? Plants miss out on all the fun of body hair, acne, and voice changes, but read on to learn about the amazing effects that hormones have on plant growth and development!

The Big Five

We’ll cover five major types of plant hormones: auxin, gibberellin, cytokinin, ethylene, and abscisic acid. These hormones can work together or independently to influence plant growth.

AUXIN

You’ve seen auxin in action. Well you haven’t seen the actual auxin molecule itself with the naked eye, but you’ve seen what it can do to a plant grown near a window. Have you ever wondered how a plant bends towards sunlight? Well, it has to do with auxin in the stem. Darwin and his son were curious about it, too. (Published in: The Power and Movement in Plants) However, they didn’t know at the time what exactly was causing plants to bend toward the light. Auxin itself wasn’t discovered until the late 1920s, and it was the first of the 5 major types of plant hormones to be studied. Auxin has lots of jobs but most importantly it stimulates growth, and if a plant doesn’t naturally produce auxin itself, it will die. So you can see auxin is pretty important. The technical alias for auxin is indole-3-acetic acid or IAA (just incase you ever see it written is “IAA” – it means the same thing as “Auxin”).

GIBBERELLIN

Gibberellin causes some similar effects in plants as auxin, but it is a very different hormone. Gibberellins were discovered originally in Japan. A fungus called Gibberella fujikuroi infected rice plants and caused them to grow too tall and fall over. The infectious fungus produced a chemical that stimulated the growth in rice plants. The chemical was isolated and named Gibberellin after the fungus. It was later found that plants naturally produce variations of these chemicals!

CYTOKININ

Who knew that fish could play a role in the discovery of a plant hormone? Aged herring sperm DNA can promote cell division. The molecule that is responsible for this was named kinetin. Soon after, a substance that had the same biological effect as kinetin was found in plants, it stimulated plant cells to divide when in culture with auxin. The substance was named cytokinin and it is involved in cell division and in the making of new plant organs, like a root or a shoot. Cytokinins are produced in the root apical meristems (very tip of the roots) and travel upward hitching a ride with water and traveling up the stem through the xylem. The movement of cytokinins is passive – it does not require energy!

Cytokinins are like the fountain of youth in plants. They delay senescence or the natural aging process that leads to death in plants. In the cell cycle, cytokinins promote the movement from the G2 phase to the M phase. In other words, they encourage cells to divide!

ETYLENE

Have you ever noticed that if you put a really ripe, brown banana right next to a bunch of green bananas, the unripe bananas will ripen and turn yellow much faster? How does that happen? Well, the brown banana is communicating with the green bananas using a hormone called ethylene. Ethylene is a plant hormone that affects ripening and rotting in plants. It is a particularly interesting plant hormone because it exists as a gas. No other plant hormone is gaseous! Ethylene can be produced in almost any part of a plant, and can diffuse through the plant’s tissue, outside the plant, and travel through the air to affect a totally different plant. How cool is that!

ABSCISIC ACID

When our bodies need water we feel thirsty. The “thirst signal” signifies that we’re dehydrated and we need a drink of water. When a plant needs water, for example during a drought, it doesn’t have too many options. A rain dance is pretty much out of the question. Plants produce a chemical messenger, called abscisic acid, to alert the rest of the plant that it is water stressed. Abscisic acid is made in droughted leaves, droughted roots, and developing seeds and it can travel both up and down in a plant stem in the xylem or phloem sounding the alarm.

That’s a brief overview on the five major types of plant hormones: auxin, gibberellin, cytokinin, ethylene, and abscisic acid. Remember that hormones are potent little chemical messengers, but they would lose their effectiveness if they hung around and built up in the tissues of the plant. So they are broken down and replaced over time.

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