(译文)Carnivorous Plants

article source:nationalgeographic
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nationalgeographic

图片文字部分的翻译部分参考自3Us


Fatal Attraction
致命诱惑

They lure insects into death traps, then gorge on their flesh. Is that any way for a plant to behave?
它们将昆虫诱入死亡陷阱后饮血啖肉。这像是植物的行为吗?

作者Carl Zimmer
摄像Helene Schmitz

Largest of its kind, the South African king sundew unfurls. Leaves of this florid species can reach two feet in length.
Drosera regia

南非帝王毛毡苔伸展开的样子,这是毛毡苔类最大的一种。这种色彩艳丽的毛毡苔,其叶子能有两英尺长。

From National Geographic
Size doesn’t ensure success. If a gluey tentacle grabs too little of a big fly, the bug may suffer injury but still struggle to freedom. In the realm of carnivorous plants, says William McLaughlin, curator at the United States Botanic Garden, “some insects aren’t digested but are still victimized.”
Drosera regia

大小不能决定捕食的成功率。如果粘稠的触须只粘到了大苍蝇的一小部分,那么这只苍蝇也许会受伤,但还是能够重获自由。美国植物园园长,William McLaughlin说,在肉食类植物的王国里,“有些昆虫虽免于殉命,但难逃受伤的厄运。”

From National Geographic
Thirsty bugs are drawn to what look like dewdrops on an Australian sundew, then find themselves entangled in sticky tentacles.
Drosera stolonifera

饥渴的虫子会被形似露珠的澳大利亚毛毡苔粘液所吸引,然后发现自己被粘稠的触须粘住了。

From National Geographic
Carnivorous plants deceive, then kill. A tropical pitcher plant smells sweet to bugs, but its slippery surfaces tumble victims into its open maw.
Nepenthes lowii

肉食性植物先伪装欺骗,再诱杀吞噬。一株热带猪笼草散发着虫子们的喜闻的芳香,但它滑不留手的表面会让虫子们跌进敞开着的无底洞里。

From National Geographic
A Venus flytrap snaps shut if its tiny hairs are brushed twice.
Dionaea muscipula

如果Venus捕蝇草的纤细毛发被触碰两次,叶子就会立即合拢。

From National Geographic
Like figures in a shadow theater, silhouettes of prey show through a Philippine pitcher plant. The waxy surface in the red tube stops bugs from climbing free. Below, enzymes leach nutrients from trapped insects.
Nepenthes alata

就像是皮影戏中的影子一样,被捕食者的轮廓也在菲律宾猪笼草内依稀可见。红色的管状叶子内,光滑的表面让虫子无法攀爬。最底下是困死的虫子,消化酶在吸收它们的营养。

From National Geographic

A hungry fly darts through the pines in North Carolina. Drawn by what seems like the scent of nectar from a flowerlike patch of scarlet on the ground, the fly lands on the fleshy pad of a ruddy leaf. It takes a sip of the sweet liquid oozing from the leaf, brushing a leg against one tiny hair on its surface, then another. Suddenly the fly’s world has walls around it. The two sides of the leaf are closing against each other, spines along its edges interlocking like the teeth of a jaw trap. As the fly struggles to escape, the trap squeezes shut. Now, instead of offering sweet nectar, the leaf unleashes enzymes that eat away at the fly’s innards, gradually turning them into goo. The fly has suffered the ultimate indignity for an animal: It has been killed by a plant.
北卡罗来纳州,一只饥饿的苍蝇在松柏林中穿梭。它被花蜜的芬芳所吸引,来到了一片绯红的花草地,然后降落在了一片肥厚的红叶上。叶子上渗出甘甜的汁液,它吸允了一口,同时一只脚也触碰到了叶子表面的一根毛发,然后又是那么一下。突然,苍蝇的整个世界变得高墙林立。两边的叶子突然合拢起来,叶边的尖刺交错咬合形成了一个牢笼。这只苍蝇挣扎着试图逃脱,但牢笼却越闭越紧。现在,美味的花蜜没有了,取而代之的是叶子分泌出的酶,将苍蝇慢慢地分解消化。作为动物,这只苍蝇可算是遭受了奇耻大辱:被一株植物杀死。

The swampy pine savanna within a 90-mile radius of Wilmington, North Carolina, is the one place on the planet where Venus flytraps are native. It is also home to a number of other species of carnivorous plants, less famous and more widespread but no less bizarre. You can find pitcher plants with leaves like champagne flutes, into which insects (and sometimes larger animals) lose themselves and die. Sundews envelop their victims in an embrace of sticky tentacles. In ponds and streams grow bladderworts, which slurp up their prey like underwater vacuum cleaners.
在北卡罗来纳州,威明顿市90英里范围内的沼泽松林生长着原生态的捕蝇草。这个地方也生长着很多其他肉食类植物,它们虽然更为常见且并不出名,但它们也同样的稀奇古怪。你可以在这里找到猪笼草,它们的叶子长得像高脚香槟杯,掉进里面的昆虫(有时是更大的动物)会丧命其中。毛毡苔将它们的猎物紧紧抱住,包裹在带有粘性的触手之中。池塘和小溪里长着狸藻,它们吸食猎物,就好像是水底的真空吸尘器。

Most carnivorous plants eat some insects for supper but need others to help them reproduce. Some carnivorous species, such as this budding sundew, can self-pollinate if no insect emissary can be enlisted.
Drosera sp.

大部分肉食类植物吞噬一些昆虫做美餐,又需要另一些昆虫来帮助它们繁衍。有些肉食类植物,就像这株发芽的毛毡苔,在没有昆虫帮助的情况下,可以自花授粉。

From National Geographic
Sensing food, a roach peers into a two-foot-tall pitcher plant. Carnivorous species photosynthesize like other plants, but most live in bogs and other nutrient-poor habitats. Enriching their diets with nitrogen captured from animals helps them thrive.
Sarracenia flava

一只蟑螂感觉到有食物在两英尺深的猪笼草里,于是爬进去窥探一番。肉食类植物和其他植物一样能进行光合作用,但是它们大多生长在沼泽或营养匮乏的地方,通过捕食动物来摄取更多的氮能帮助它们旺盛地生长。

From National Geographic
To avoid capturing and consuming prospective pollinators, pitcher plants keep their flowers far away from their traps via long stalks.
Sarracenia hybrid

为了避免误食传粉的昆虫。猪笼草将花用过长茎长到远离陷阱的地方。

From National Geographic
Blooms hang upside down like Chinese lanterns, luring bees into an elaborate pollen chamber.
Sarracenia flava

花朵向下生长就好像一个灯笼,将蜜蜂吸引到精心打造的花粉室。

From National Geographic
A glassy cellar spider contends with the glistening tentacle tips of a South African king sundew. The more the arachnid struggles, the more likely it is to become mired in the thick mucilage globules at the ends of the tiny stalks. When the spider gives up, either from exhaustion or suffocation, it will be conveyed by the tentacle to the leaf’s center. There burning acids and enzymes will reduce its body to a nutrient soup easy for the plant to digest.
Drosera regia (sundew); Pholcus phalangioides (spider)

一只光滑的地窖蜘蛛(cellar spider)正与南非帝王毛毡苔闪闪发亮的触须展开生死搏斗。这只长脚蜘蛛越是挣扎,在厚厚的粘夜里越陷得深。当蜘蛛放弃努力,不管是精疲力竭还是窒息而亡,触须都会将它运送到叶子中心。然后强酸和酶会将它的身体变为一道营养丰富的浓汤,这样更便于植物吸收。

From National Geographic
A wolf spider treads perilously on the rim of a South American pitcher plant, perhaps looking to prey on insects drawn to the plant’s strong nectar scent. William McLaughlin, curator of the U.S. Botanic Garden, notes that spiders like this one are opportunists, often building webs directly over the mouths of pitcher plants. “It’s a great strategy,” he says, “so long as they don’t fall in themselves.”
Heliamphora nutans (pitcher plant); family Lycosidae (spider)

一只狼蛛在南非猪笼草边缘走着,这相当危险,他正在寻找被浓郁花香吸引过来的昆虫。William McLaughlin,美国植物园园长说,像这种蜘蛛,就是典型的机会主义者。他们把网直接结在猪笼草的血盆大口上。“这也是极好的方法,”他说,“只要别把自己也搭进去了。”

From National Geographic
Many of the world’s 675-plus carnivorous species set passive traps. A bun-size butterwort bristles with gluey hairs that ensnare insects until digestive juices do their work.
Pinguicula ‘Hans’

食肉类植物约有675多种,很多都会守株待兔。一株面包大小的捕虫瑾,长满了粘稠的茸毛,它们将昆虫犹如陷阱,直至分泌消化液才合拢。

From National Geographic
A pale green butterfly senses nectar and alights on a rare California pitcher plant. Also called a cobra lily for its bulbous head, forked tongue, and long tubular pitcher, it grows in mountainous parts of the West Coast and is an oddity among its kind. Although it traps prey in a manner similar to other pitcher plants, its leaves contain no digestive enzymes. Instead, it relies on symbiotic bacteria to turn captured insects into usable nutrients.
Darlingtonia californica

一只淡绿色蝴蝶闻香而来,停落在一株罕见的加利福尼亚猪笼草上。该种猪笼草呈球茎,叶子分叉且呈长管状,所以又称眼镜蛇百合。它生长在西海岸多山地区,属于同种物种中的异类。虽然它捕捉猎物方式和其他猪笼草相似,但是它不会分泌消化酶,所以需要借助共生细菌,将被困昆虫转变为可供食用的营养物质。

From National Geographic
The thimble-size west Australian pitcher plant has a taste for insects that crawl. Its guide hairs and cloying scent encourage ants to clamber into its digestive depths.
Cephalotus follicularis

套圈模样的澳大利亚猪笼草对爬行类昆虫的口味更情有独钟.它的毛发和甘甜的气息诱惑着蚂蚁爬到叶子的深处,那里生产着消化液.

From National Geographic

There is something wonderfully unsettling about a plant that feasts on animals. Perhaps it is the way it shatters all expectation. Carl Linnaeus, the great 18th-century Swedish naturalist who devised our system for ordering life, rebelled at the idea. For Venus flytraps to actually eat insects, he declared, would go “against the order of nature as willed by God.” The plants only catch insects by accident, he reasoned, and once a hapless bug stopped struggling, the plant would surely open its leaves and let it go free.
植物以动物为食这件事十分令人震惊。这可能是因为这种行为和我们预想的常态相悖。Carl Linnaeus,18世纪伟大的瑞典自然学家,发明了生物的分类方式,在这一点上却没有始终一贯。拿捕蝇草来说,它确实捕食昆虫,Carl Linnaeus却宣称这将“违背作为上帝意志体现的自然规律。”他解释说,植物只是在偶然的情况下捕捉到昆虫,而且一旦一只倒霉的虫子停止挣扎,植物就肯定会打开叶子放走它。

Carnivorous plants lure some insects for prey but attract others for the more benign task of propagation. Heliamphora minor, which grows in the highlands of southern Venezuela, is one of the smallest pitcher plants in the world. Flower color and position signal to insects the blossom’s degree of maturity. The white color of the upside-down flower here indicates its readiness to be pollinated, while its umbrella shape protects powdery pollen from washing off in heavy rains. The burgundy bloom to its left has presumably been pollinated. The green, horizontal blossom below is still too immature to benefit from insect visitors.
Heliamphora minor

食肉植物吸引昆虫,有些是为了捕猎,有些则是为了繁衍后代。Heliamphora minor,生长在委内瑞拉南部高地上,是世界上最小猪笼草之一。花色和位置,向昆虫传递着花株成熟程度的信息。倒挂的白色花蕾表明已可以接受授粉,而伞形能够保护花粉免受暴雨侵袭。其左边酒红花蕾,可能象征着授粉完毕。和其平行的下方绿色花蕾表示尚未成熟,即便有昆虫来造访也无济于事。

From National Geographic
A water-filled North American hybrid tempts bees with the promise of nectar and a rim that looks like a prime landing pad. Carnivory is not the most efficient way for a plant to secure nutrients, but it is certainly among the most exotic.
Sarracenia hybrid

一株装满液体的混种肉食植物用貌似花蜜的消化液吸引来蜜蜂,又用看似降落平台的花瓣来促其滑倒。食肉并不是植物获得营养最高效的方法,但肯定是最奇异的方法之一。

From National Geographic

Charles Darwin knew better, and the topsy-turvy ways of carnivorous plants enthralled him. In 1860, soon after he encountered his first carnivorous plant—the sundew Drosera—on an English heath, the author of Origin of Species wrote, “I care more about Drosera than the origin of all the species in the world.” He spent months running experiments on the plants. He dropped flies on their leaves and watched them slowly fold their sticky tentacles over their prey. He excited them with bits of raw meat and egg yolk. He marveled how the weight of just a human hair was enough to initiate a response. “It appears to me that hardly any more remarkable fact than this has been observed in the vegetable kingdom,” he wrote. Yet sundews ignored water drops, even those falling from a great height. To react to the false alarm of a rain shower, he reasoned, would obviously be a “great evil” to the plant. This was no accident. This was adaptation.
Charles Darwin对此了解得更为深刻,肉食性植物的种种匪夷所思的表现令他痴迷不已。他是在英国的某处荒野第一次遇见了肉食性植物——Drosera毛毡苔,没过多久,在1860年,这位《物种起源》的作者如是写到,“我对Drosera毛毡苔兴趣远胜于世上的物种起源之谜。”他花费数月时间在这些植物上做实验。他将苍蝇丢到Drosera毛毡苔的叶子上,然后观察它们粘稠的触须慢慢裹住它们的猎物。他还用少量生肉和蛋黄来刺激它们的食欲。实验发现即使只有一根头发的重量也足够Drosera毛毡苔做出反应,对此他啧啧称奇并写到“我来讲在对植物王国的观察中几乎没什么比更吸引人的了。”但是毛毡苔无视水滴的影响,即使那些水滴从高处落下,重重砸在毛毡苔上。他解释道,对雨水造成的误报做出反应,是植物的大忌。这并不是巧合。这是进化的必然结果。

Darwin expanded his studies from sundews to other species, eventually recording his observations and experiments in 1875 in a book, Insectivorous Plants. He marveled at the exquisite quickness and power of the Venus flytrap, a plant he called “one of the most wonderful in the world.” He showed that when a leaf snapped shut, it formed itself into “a temporary cup or stomach,” secreting enzymes that could dissolve the prey. He noted that a leaf took more than a week to reopen after closing and reasoned that the interlocking spines along the margin of the leaf allowed undersized insects to escape, saving the plant the expense of digesting an insufficient meal. Darwin likened the hair-trigger speed of the Venus trap’s movement—it snaps shut in about a tenth of a second—to the muscle contraction of animals. But plants don’t have muscles and nerves. So how could they react like animals?
Darwin的研究领域慢慢从毛毡苔扩展到其他物种,最终在1875年他将他的观察和实验所得成果记录在了《食虫植物》一书中。他对捕蝇草的速度之快、力量之大颇为惊叹,称其为“世上最神奇的东西之一。”他在书中展示了捕蝇草,当他们的叶子合拢后就形成了一个“临时的胃”,其中会分泌酶来消化猎物。他还记录到一片叶子要花一个多星期的时间才会重新打开,而叶子合拢时交错咬合的叶边尖刺会让小体型的昆虫逃脱,这是因为费力来消化一份无法饱腹的食物是得不偿失的。捕蝇草叶面上的毛发(相当于一个触发器)能在十分之一秒内让叶子闭合,其速度完全可以和动物肌肉收缩的速度相媲美。但植物可没有肌肉和神经。所以它们是如何做到像动物那般快速的反应呢?

A snail makes solemn progress up the rolled leaf of a yellow pitcher plant. Some scientists think the stalk’s squiggly vertical vein is a ladder intended to guide crawling food to the plant’s mouth. Others say it’s a structural reinforcement. Members of this skinny species can grow to three feet in height and tip over when overfilled with rainwater and the husks of prey.
Sarracenia flava (pitcher plant); family Helicidae (snail)

一只蜗牛在黄猪笼草的叶子上缓慢而坚定地向上攀爬。一些科学家认为,这些弯弯曲曲的经络起着梯子的作用,将它们的美餐引入到嘴边。另一些科学家则认为这种构造起到了强化结构的作用。这种细长的植物能长到3英尺高,当叶子里灌满雨水或者塞满了昆虫外壳时会伏倒下来。

From National Geographic

Today biologists using 21st-century tools to study cells and DNA are beginning to understand how these plants hunt, eat, and digest—and how these bizarre adaptations arose in the first place. After years of study, Alexander Vol kov, a plant physiologist at Oakwood University in Alabama, believes he has figured out the Venus flytrap’s secret. “This,” Volkov declares, “is an electrical plant.”
当今生物学家利用21世纪的先进工具,在研究了细胞和DNA后开始逐渐了解了这些植物是如何进行捕食、消化以及它们这种古怪的特点最初是如何产生的。经过多年的研究,Oakwood大学的植物生理学家Alexander Vol kov相信他破解了捕蝇草的秘密。“这种植物,”他说,“是一株电子植物。”

When an insect brushes against a hair on the leaf of a Venus flytrap, the bending triggers a tiny electric charge. The charge builds up inside the tissue of the leaf but is not enough to stimulate the snap, which keeps the Venus flytrap from reacting to false alarms like raindrops. A moving insect, however, is likely to brush a second hair, adding enough charge to trigger the leaf to close.
当昆虫触碰了捕蝇草表面的毛发而使其发生扭曲,这种扭曲触发了少量的电荷。这些电荷在叶内组织中积累起来但还不足以造成叶子的闭合,这避免了捕蝇草对一些无谓的刺激作出反应,比如像雨水。而一只昆虫则很可能因为不停移动而触碰到另一根叶子表面的毛发,这样积累起来的电荷就足够使叶子闭合起来。

Volkov’s experiments reveal that the charge travels down fluid-filled tunnels in a leaf, which opens up pores in cell membranes. Water surges from the cells on the inside of the leaf to those on the outside, causing the leaf to rapidly flip in shape from convex to concave, like a soft contact lens. As the leaves flip, they snap together, trapping an insect inside.
Volkov的实验表明:电荷在充满液体的叶子内部自由移动,使细胞膜上的毛孔打开。水从细胞内部涌出到细胞外部,造成叶子的形状迅速转变,由饱满变得凹陷,就好像柔软的隐形眼镜镜片一样。当叶子转换形状时,它们就合拢起来,将昆虫困在其中。

The bladderwort has an equally sophisticated way of setting its underwater trap. It pumps water out of tiny bladders, lowering the pressure inside. When a water flea or some other small creature swims past, it bends trigger hairs on the bladder, causing a flap to open. The low pressure sucks water in, carrying the animal along with it. In one five-hundredth of a second, the door swings shut again. The cells in the bladder then begin to pump water out again, creating a new vacuum.
狸藻的水下陷阱有着同样复杂的构造。它将小囊中的水排出,降低了内部压强。当有水蚤或者其他类似的小东西游过时,会触碰到它的毛发,然后小囊的封口会打开。囊中因为压强低,水流会顺势进入,将小动物一并带入。在五百分之一秒后,封口又会迅速闭上。狸藻中的细胞随后继续开始排水,又再次形成真空状态。

Lurking half-submerged in bogs and sandbanks of the southeastern United States, the parrot pitcher plant has an appetite for arthropods, ants, and slugs. Prey are drawn to nectar inside the hood and by light shining through a latticework of “windows.” Needlelike, downward-pointing hairs line the interior, making retreat impossible—and directing prey to the plant’s acidic depths.
Sarracenia psittacina

鹦鹉猪笼草生长在美国东南部的沼泽和沙洲,将半个身子潜伏起来,喜食节足动物、蚂蚁、蛞蝓。它们的猎物会被花蜜吸引到形似罩子的叶子里,阳光照射下的它们会在格子状的“窗子”里若隐若现。里面长满了头部向下的针状细毛,所以想退出去是不可能的,只能顺着细毛的方向走,终点是满布酸液的叶子内部。

From National Geographic

Many other species of carnivorous plants act like living flypaper, snagging animals on sticky tentacles. Pitcher plants use yet another strategy, growing long tube-shaped leaves into which insects fall. Some of the largest have pitchers up to a foot deep and can consume a whole frog or even a rat unlucky enough to fall into them. Sophisticated chemistry helps make the pitcher a death trap. Nepenthes rafflesiana, a pitcher plant that grows in jungles on Borneo, produces nectar that both lures insects and forms a slick surface on which they can’t get a grip. Insects that land on the rim of the pitcher hydroplane on the liquid and tumble in. The digestive fluid in which they fall has very different properties. Rather than being slippery, it’s gooey. If a fly tries to lift its leg up into the air to escape, the fluid holds on tenaciously, like a rubber band.
很多其他肉食性植物就像是活生生的捕蝇纸,用粘稠的触须将动物钩挂住。但猪笼草用的是另一套方法,它长出像长管一样的叶子让昆虫掉落其中。最大型的猪笼草,其叶子形成的“壶”有一英尺深,这足以消化掉在里面的青蛙或者哪只倒霉透顶的老鼠。复杂的化学特性使猪笼草成为了一个死亡陷阱。Nepenthes rafflesiana,一种长在Borneo丛林中的猪笼草会制造花蜜来诱惑昆虫,同时形成一个光滑的表面,昆虫在上面完全站不住脚。降落在猪笼草上的昆虫会在“花蜜”上失控打滑,跌落“壶”中。它们跌落在消化液里,这些消化液和“花蜜”的特性全然不同。不但一点不滑,反而相当有粘性。如果一只苍蝇试图蹬脚逃脱,这些液体会像橡皮筋一样将它牢牢箍住。

Many carnivorous plants have special glands that secrete enzymes powerful enough to penetrate the hard exoskeleton of insects so they can absorb nutrients from inside their prey. But the purple pitcher plant, which lives in bogs and infertile sandy soils in much of North America, enlists other organisms to digest its food. It is home to an intricate food web of mosquito larvae, midges, protozoans, and bacteria, many of which can survive only in this unique habitat. The animals shred the prey that fall into the pitcher, and the smaller organisms feed on the debris. Finally, the pitcher plant absorbs the nutrients released by the feeding frenzy. “Having the animals creates a processing chain that speeds up all the reactions,” says Nicholas Gotelli of the University of Vermont. “And then the plant dumps oxygen back into the pitcher for the insects. It’s a tight feedback loop.”
很多肉食性植物都有特殊的腺体以分泌酶,而这些酶相当强大,足以穿透昆虫坚硬的外壳,这样它们就能吸收猎物体内的营养了。但是紫猪笼草会利用其它微生物来帮助它消化食物,它们大多生活在北美沼泽地区和贫瘠沙地。这里有着复杂的食物链,蚊子幼虫,蠓,单细胞生物和细菌,它们很多只能在这个特殊的栖息地生存。动物将它们的猎物撕碎后会有残渣掉进猪笼草,于是微生物开始食用这些残渣。它们疯狂进食时产生的营养素最终被猪笼草所吸收。“通过动物的参与,这条生态链的转化速度大大加快,”Vermont大学的Nicholas Gotelli说。“然后植物将氧气返还给猪笼草中的昆虫,这是一个相当紧凑的循环。”(译者注:这个生物链循环的逻辑没怎么读懂,氧气返还给猪笼草中的昆虫也算是个循环吗?不给不是更好?)

Pitcher plants grow by the thousands in the bogs at the Harvard Forest in central Massachusetts. One late spring day Aaron Ellison took me on a tour, stopping from time to time to watch patiently as I pulled a sinking leg out of the muck. “You haven’t had a real bog experience till you’re up to your crotch in it,” said Ellison, a senior ecologist at the forest. Little orange flags fluttered across the bogs. Each one marked a pitcher plant impressed into the service of science. In the distance a student was feeding flies to the flagged plants. The researchers raise these insects on food spiked with unusual forms of carbon and nitrogen so they can later harvest the pitcher plants and measure how much of each element from the flies has been absorbed into the plants. Because pitcher plants grow slowly (they can live for decades), the experiments can take years to yield results.
在Massachusetts中部Harvard森林的沼泽中生长着数以千计的猪笼草类植物。春末的某天,Aron Ellison——这片森林中资深的生态学家,带我游览了一番,他不时停下脚步耐心观察地形,而我却频频陷入烂泥之中,举步维艰。“如果你没有过大半个身子陷入泥沼的经历,就谈不上对沼泽有什么真切地体会了,”Ellison说到。沼泽地里飘动着一面面桔黄色的小旗。每个都标记了一株供科学研究用的猪笼草。不远处的一个学生正在用苍蝇喂食这其中的一株。研究人员用添加了特别碳、氮成分的食物来喂养这些昆虫,这样他们就能从随后收集到的猪笼草里测出每种成分被植物吸收了多少。因为猪笼草生长缓慢(它们可以存活数十年),这项实验可能要花数年才能得出结果。

Ellison and Gotelli are trying to figure out what evolutionary forces pushed these plants toward a taste for meat. Carnivorous plants clearly benefit from eating animals; when the scientists feed pitcher plants extra bugs, the plants get bigger. But the benefits of eating flesh are not the ones you might expect. Carnivorous animals like ourselves use the carbon in protein and the fat in meat to build muscles and store energy. Carnivorous plants instead draw nitrogen, phosphorus, and other critical nutrients from their prey in order to build light-harvesting enzymes. Eating animals, in other words, lets carnivorous plants do what all plants do: grow by grabbing energy directly from the sun.
Ellison和Gotelli试图找出是怎样的进化力量使得这些植物对肉类有了兴趣。肉食类植物显然从进食动物中获得了好处;当科学家们对猪笼草喂食更多的昆虫时,这些植物长得更大了。不过食用肉类的好处可能和你所想的并不一样。肉食类动物,就好象我们人类自己,会使用蛋白质中的碳和肉中的脂肪来构建我们的肌肉并储存能量。肉食类植物则是吸收猎物体内氮、磷及其他重要营养来制造光合作用所需要的酶。捕食动物,换言之,是为了让肉食类植物能像其他任何植物一样:通过植物从太阳哪里吸取营养来成长。

Alas, they do a lousy job of it. Carnivorous plants turn out to be very inefficient at converting sunlight into tissue. That’s because they have to use a lot of energy to make the equipment they need to catch animals—the enzymes, the pumps, the sticky tentacles, and so on. A pitcher or a flytrap cannot carry out much photosynthesis because, unlike plants with ordinary leaves, they do not have flat solar panels that can grab lots of sunlight. Ellison and Gotelli suspect that only under special conditions do the benefits of carnivory outweigh the costs. The poor soil of bogs, for example, offers little nitrogen and phosphorus, so carnivorous plants enjoy an advantage there over plants that obtain these nutrients by more conventional means. Bogs are also flooded with sunshine, so even an inefficient carnivorous plant can carry out enough photosynthesis to survive. “They’re stuck, and they’re making the best of it,” says Ellison.
唉,可惜它们的这项活做得实在太糟糕了。事实证明,肉食类植物的光和转化能力异常低下。这是因为他们要使用相当多的能量来构造它们捕食动物所需的工具——酶,“水泵”,粘稠的触手等等。一株猪笼草或者捕蝇草没法携带大量磷,因为不像其他植物,它们没有扁平的叶子来获得大量的阳光。Ellison和Gotelli推测,只有在特定情况下,食肉带来的好处才不会显得徒劳无益。沼泽也经常会被阳光曝晒,所以即使是光合作用能力低下的肉食性植物也能得以生存。“它们难以动弹,而它们已经尽力而为了,”Ellison说。

Evolution has repeatedly made this trade-off. By comparing the DNA of carnivorous plants with other species, scientists have found that they evolved independently on at least six separate occasions. Some carnivorous plants that look nearly identical turn out to be distantly related. Both kinds of pitcher plants—the tropical genus Nepenthes and the North American Sarracenia—grow deep pitcher-shaped leaves and employ the same strategy for capturing prey. Yet they evolved from different ancestors.
生物进化不断地做着这样的制约权衡。通过比较肉食类植物和其他物种的DNA,科学家们发现它们是分六个不同时期进化出相异的特质。(译者注:后半句原文没怎么读懂。)有些肉食类植物看起来很雷同,其实是风马牛不相及,两种猪笼草类植物——热带的Nepenthes和北美的Sarracenia——都长有长壶状的叶子,使用相同的技巧来捕捉猎物。但是他们的祖先完全不同。

A cave cricket is caught in the sticky clutches of a king sundew.
Drosera regia (sundew); family Gryllacrididae (cricket)

一只洞穴蟋蟀被帝王毛毡苔粘稠的触须抓住了。

From National Geographic
The trapped insect struggles to free itself.
Drosera regia (sundew); family Gryllacrididae (cricket)

被困住的蟋蟀奋力挣扎。

From National Geographic
Possibly injured but certainly fortunate, the cricket plummets to freedom. “Whether a bug will get away or not is a mortal battle decided in moments,” says Barry Rice, a botanist at the University of California, Davis.
Drosera regia (sundew); family Gryllacrididae (cricket)
From National Geographic

In several cases scientists can see how complex carnivorous plants evolved from simpler ones. Venus flytraps, for example, share an ancestor with Portuguese sundews, which only make passive flypaper glands on their stems. They share a more recent ancestor with Drosera sundews, which not only make flypaper glands but can also curl their leaves over their prey. Venus flytraps appear to have evolved an even more elaborate version of this kind of trap, complete with jawlike leaves.
在其他一些个例中,科学家们发现肉食性植物可以从极其简单的构造进化为纷繁复杂。举例来说,Venus捕蝇草和Portuguese毛毡苔是同宗同源,而后者只会在茎部被动地产生粘性腺体。Portuguese毛毡苔和Drosera毛毡苔关系更为接近,而Drosera毛毡苔不但会产生粘性腺体,而且还会卷曲叶子包裹住猎物。Venus捕蝇草似乎是这种类型的陷阱的升级进化版,额外拥有了齿状的叶子。

Unfortunately, the adaptations that enable carnivorous plants to thrive in marginal habitats also make them exquisitely sensitive to environmental changes. Agricultural runoff and pollution from power plants are adding extra nitrogen to many bogs in North America. Carnivorous plants are so finely tuned to low levels of nitrogen that this extra fertilizer is overloading their systems. “They eventually burn themselves out,” says Ellison.
不幸的是,肉食性植物演化出的适应性既使它们在毫不起眼的栖息地生长得欣欣向荣,也使它们对环境的变化异常敏感。在北美洲,农业排水和电厂污染使得沼泽中的氮含量激增。肉食性植物对低浓度的氮含量有极佳的偏好,这些多出来的营养物会使它们构造系统无法承受。“它们最终会发生自燃,”Ellison说。

Humans also threaten carnivorous plants in other ways. The black market trade in exotic carnivorous plants is so vigorous now that botanists are keeping the location of some rare species a secret. Venus flytraps are being poached from North Carolina by the thousands to be sold at roadside stands. The North Carolina Department of Agriculture has been dabbing wild Venus flytraps with harmless dye that’s normally invisible but glows in UV light so that inspectors who come across Venus flytraps for sale can quickly determine if the plants were raised in a greenhouse or poached from the wild. But even if the poaching of carnivorous plants can be halted (a very big if), they will continue to suffer from other assaults. Their habitat is disappearing, to be replaced by shopping centers and houses. Fires are being suppressed, allowing other plants to grow quickly and outcompete the Venus flytraps. Good news, perhaps, for flies. But a loss for all who delight in the sheer inventiveness of evolution.
而其他方面,人类也在威胁着肉食类植物的生存。黑市对这些奇异的植物情有独钟,需求旺盛,植物学家们对一些稀有物种的栖息地秘而不宣。北卡罗来纳州的Venus捕蝇草被成千上万地偷偷采摘,然后在路边叫卖。北卡罗来纳州农业部已经将野生的Venus捕蝇草上打上了无害的印记,这种印记一般看不出来,但是在紫外线下会微微发光,这样巡视员偶然碰到了贩卖Venus捕蝇草的人就可以迅速确定这株植物是人工培养的还是从野外偷摘的。但是即使偷摘的行为能够被制止(这还要打上个大大的问号),它们还是会受到伤害。它们的栖息地正在逐渐消失,取而代之的是购物中心和房屋。由于严禁烟火,其他植物可以生长的更快而在竞争中胜过Venus捕蝇草。(译者注:不是很能理解原文。也许是因为捕蝇草生长在沼泽中,所以如果起火不易受到牵连?)对苍蝇来说,这可能是个好消息。对乐于见到大自然在进化过程中极尽精妙创作之能的人来说就是一种损失了。

Most famous and fascinating of all carnivorous plants, the Venus flytrap uses electricity to capture unsuspecting prey. When one or more of its surface hairs are brushed twice—an energy-conserving system that distinguishes prey from other stimuli—an electrical charge signals cells on the outside of the leaf to expand, swiftly warping the shape of the plant’s thumbprint-size lobes from convex to concave and snapping them shut. The hairlike spikes on the end of the lobes, called cilia, then mesh together inexactly, letting small prey escape but trapping prizes large enough to be worth digesting.
Dionaea muscipula

最神奇、最广为人知的肉食性植物——Venus捕蝇草,它们运用电子的原理来捕食毫无戒心的猎物。当它们叶表的一根或多根毛发被触碰两次,它们就会识别出猎物,而不会将其和其他刺激物相混淆,再通过能量积累机制,电流冲击的信号叶子外表面的细胞迅速膨胀,拇指大小的叶子形状会马上扭曲,由饱满变得凹陷,两边猛的闭合起来。叶子边缘,像头发一样的尖刺(准确的说是纤毛),略显凌乱地相互咬合起来,体型小的猎物可能逃脱,但会把大到值得一吃的猎物困住。

From National Geographic

p.s1: 图床在Picasa,已彻底被墙,请自备翻墙工具或参见原文或纯文字阅读。

p.s2: 无责任翻译,文章译后也只审过一遍。有异议者请参见原文,用自己的智商理解,勿盲信。

p.s3: 这是3月份那期里的文章,因为一直被有些事搁着,所以始终没能动笔。得到的教训是:时间宝贵,做什么都拖拉不得。

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