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listen to part of a lecture in a botany class.

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So we\'ve been looking at varieties of carnivorous plant species,

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plants that capture and consume insects.

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And today I\'d like to introduce another

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one that\'s often referred to as the pitcher plant.

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The scientific name for the pitcher plant is Nepenthes.

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The 100 or so species of Nepenthes found in the forests of Southeast Asia have a variety of shapes and sizes,

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but since the soil there generally lacks adequate nutrients,

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these plants need to supplement the nutritional intake of their roots.

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And how do they do this?

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Well, they have pitchers, modified leaves that are filled with fluid that act as traps for insects,

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which fall into this fluid and are digested there to supply additional nutrition for the plant.

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Now, at first, it appears that the Nepenthes method of catching prey, mostly ants, is pretty basic,

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that the pitcher part of the plant is a passive pitfall trap that any unsuspecting ant might just slip down into.

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And this has been the long held view of botanists,

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but investigation in the forests of Borneo has revealed that some Nepenthes are far more active in catching their prey than previously thought.

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Okay, first of all, there\'s a rim around the top of the pitcher.

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This is called the Para stone.

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And along the inside of the Para stone are glands that secrete a sweet nectar that

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well, it\'s the smell of this nectar that lures the prey into the pitcher

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and inside the pitcher just below the peristome, botanists noticed a waxy layer, one that\'s smooth and slippery,

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and as insects climb inside to get the nectar,

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this waxy layer prevents them from maintaining a foothold,

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so they fall into the liquid below and are unable to climb back up and escape.

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For a long time, this waxy zone was thought to be essential for the plant to trap its prey,

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but recently, observation of these plants in the lab revealed that insects often fall into the pitcher without ever touching the waxy layer,

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and Even more surprising was the discovery that some species of Nepenthes don\'t even have this layer.

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That\'s right, some species have this layer, but others don\'t,

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and the species without the waxy layer are just as effective at catching prey.

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Well, botanists were curious about this, of course,

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so some of them went into the forests of Borneo to videotape plants like these ones without a waxy lair,

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and they observed again and again that most of the ants that climbed onto a Nepenthes parastome Simply wandered off again unharmed.

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But one day, the researchers returned to the study site after a rainstorm

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and were surprised to see that every ant that stepped onto one of these peristomes slipped right down into the pitcher,

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and when they looked into the pitcher, they noticed lots of ants already trapped there.

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They also observed that the parastomes were wet,

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which is unusual, since plant surfaces usually repel water.

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But it turns out that when the parastome of one of these Nepenthes plants is wet.

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It holds water so its surface gets extremely slippery,

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and insects slide right off and drop down into the trap.

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And the researchers discovered something else too,

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that the parastomes were wet from early evening until early morning, whether it was raining or not.

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And this didn\'t seem to be simply the result of water condensing from the air as it got cooler.

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Researchers also noticed an increase in the amount of nectar produced in the evening,

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and tests showed that nectar absorbs moisture from the air,

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and this helps keep the rim wet.

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One researcher suggested yet another possibility,

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a plant may even regulate the degree of wetness by changing the amount of nectar it secretes hard to believe.

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Well, there\'s more.

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Most botanists had assumed that carnivorous plants were always ready to catch prey,

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but here we have a plant with a trapping mechanism that is dependent, or at least in part on the weather,

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and that sometimes works and sometimes doesn\'t.

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How could that be effective?

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Well, some of these researchers hypothesize

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that it\'s for the same reason some animals hunt only intermittently

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to make it more difficult for prey to predict their attacks,

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because then prey could develop countermeasures to avoid them.

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For example, ants often send lone scouts out to search for food.

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If a scout finds some and returns unharmed, it alerts other ants, which then stream out to find the source of the food.

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It\'s possible that when these ants reach the Nepenthes plant, its peristone will be wet,

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so instead of finding food,

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they\'ll be the Nepenthes main course.

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