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1 .listen to part of a lecture in a botany class.
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2 .So we\'ve been looking at varieties of carnivorous plant species,
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3 .plants that capture and consume insects.
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4 .And today I\'d like to introduce another
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5 .one that\'s often referred to as the pitcher plant.
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6 .The scientific name for the pitcher plant is Nepenthes.
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7 .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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8 .but since the soil there generally lacks adequate nutrients,
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9 .these plants need to supplement the nutritional intake of their roots.
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10 .And how do they do this?
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11 .Well, they have pitchers, modified leaves that are filled with fluid that act as traps for insects,
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12 .which fall into this fluid and are digested there to supply additional nutrition for the plant.
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13 .Now, at first, it appears that the Nepenthes method of catching prey, mostly ants, is pretty basic,
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14 .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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15 .And this has been the long held view of botanists,
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16 .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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17 .Okay, first of all, there\'s a rim around the top of the pitcher.
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18 .This is called the Para stone.
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19 .And along the inside of the Para stone are glands that secrete a sweet nectar that
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20 .well, it\'s the smell of this nectar that lures the prey into the pitcher
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21 .and inside the pitcher just below the peristome, botanists noticed a waxy layer, one that\'s smooth and slippery,
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22 .and as insects climb inside to get the nectar,
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23 .this waxy layer prevents them from maintaining a foothold,
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24 .so they fall into the liquid below and are unable to climb back up and escape.
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25 .For a long time, this waxy zone was thought to be essential for the plant to trap its prey,
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26 .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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27 .and Even more surprising was the discovery that some species of Nepenthes don\'t even have this layer.
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28 .That\'s right, some species have this layer, but others don\'t,
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29 .and the species without the waxy layer are just as effective at catching prey.
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30 .Well, botanists were curious about this, of course,
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31 .so some of them went into the forests of Borneo to videotape plants like these ones without a waxy lair,
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32 .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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33 .But one day, the researchers returned to the study site after a rainstorm
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34 .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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35 .and when they looked into the pitcher, they noticed lots of ants already trapped there.
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36 .They also observed that the parastomes were wet,
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37 .which is unusual, since plant surfaces usually repel water.
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38 .But it turns out that when the parastome of one of these Nepenthes plants is wet.
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39 .It holds water so its surface gets extremely slippery,
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40 .and insects slide right off and drop down into the trap.
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41 .And the researchers discovered something else too,
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42 .that the parastomes were wet from early evening until early morning, whether it was raining or not.
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43 .And this didn\'t seem to be simply the result of water condensing from the air as it got cooler.
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44 .Researchers also noticed an increase in the amount of nectar produced in the evening,
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45 .and tests showed that nectar absorbs moisture from the air,
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46 .and this helps keep the rim wet.
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47 .One researcher suggested yet another possibility,
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48 .a plant may even regulate the degree of wetness by changing the amount of nectar it secretes hard to believe.
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49 .Well, there\'s more.
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50 .Most botanists had assumed that carnivorous plants were always ready to catch prey,
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51 .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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52 .and that sometimes works and sometimes doesn\'t.
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53 .How could that be effective?
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54 .Well, some of these researchers hypothesize
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55 .that it\'s for the same reason some animals hunt only intermittently
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56 .to make it more difficult for prey to predict their attacks,
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57 .because then prey could develop countermeasures to avoid them.
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58 .For example, ants often send lone scouts out to search for food.
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59 .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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60 .It\'s possible that when these ants reach the Nepenthes plant, its peristone will be wet,
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61 .so instead of finding food,
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62 .they\'ll be the Nepenthes main course.
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