Lecture: The Pitcher of Nepenthes: Narrator: Listen to part of a lecture in a botany class. Professor: So we've been looking at varieties of carnivorous plant species, plants that capture and consume insects. And today I'd like to introduce another. One that's often referred to as the pitcher plant. The scientific name for the picture plant is nepenthes. A hundred or so species of nepenthes found in the forests of Southeast Asia have a variety of shapes and sizes. But since the soil there generally lacks adequate nutrients, these plants need to supplement the nutritional intake of the roots. And how do they do this? Well, they have pitchers, modified leaves that are filled with fluid that act as traps for insects which fall into this fluid and are digested there to supply additional nutrition for the plant. Now, at first it appears that the nepenthes' method of catching pray, mostly ants is pretty basic, that the pitcher part of the plant is a passive pitfall trap that any unsuspecting ant might just slip down info. And this has been a long held view of botanists. But investigation in the forest of Borneo has revealed that some nepenthes are far more active in catching their prey than previously thought. Okay. First of all, there's a rim around the fop of the pitcher. This is called the Peristome. And along the inside of the Peristome are glands that secrete a sweet nectar that. Well, it's the smell of this nectar that lures the prey into the pitcher. And inside the pitcher just below the Peristome, botanists notice to a waxy layer, one that's smooth and slippery. And its insects dime inside to get the nectar. This waxy layer prevents them from maintaining a foothold. so they fall info the liquid below and are unable to climb back up and escape. For a long time this waxy zone was thought to be essential for the plant to trap its pray. But recently, observation of these plants in the lab revealed that insects often fall info the pitcher without ever touching the waxy layer. And even more surprising was the discovery that some species of nepenthes don't even have this layer. That's right. Some species have this layer, but others don't. And the species without the waxy layer are just as effective in catching prey. Well, botanists were curious about this of course. So some of them went into the forests of Borneo to videotape plants like these, ones without a waxy layer. And they observed again and again that most of the ants that climbed onto nepenthes Peristome simply wandered off again, unharmed. But one day the researchers returned to the study site after a rain storm and were surprised to see that every ant that stepped onto one of these peristomes slipped right down into the pitcher. And when they looked into the pitcher, they noticed lots of ants already trapped there. They also observed that the peristomes were wet, which is unusual, since plant surfaces usually repel water. But it turns out that when the Peristome of one of these nepenthes plants is wet, it holds water. So its surface gets extremely slippery and insects slide right off and drop down into the trap. And the researchers discovered something else too. That the peristomes were wet from early evening until early morning whether it was raining or not. And this didn't seem to be simply the result of water condensing from the air and it gets cooler. Researchers also noticed an increase in the amount of nectar produced in the evening. And tests showed that nectar absorbs moisture from the air and this helps keep the rim wet. One researcher suggested yet another possibility. A plant may even regulate the degree of wetness by changing the amount of nectar it secrets. Hard to believe? Oh, there's more, most botanists had assumed that carnivorous plants were always ready to catch prey, but here we have a plant with the trapping mechanism that is dependent or at least in part on the weather and it sometimes works and sometimes doesn't. How could that be effective? Well, some of these researchers hypothesize that it's for the same reasons some animals hunt only intermittently to make if more difficult for prey to predict their attacks, because then prey could develop countermeasures to avoid them. For example, ants often send lone scouts to search for food. If a scout find some and returns unharmed, it alerts other ants which then stream out to find a source of the food, it's possible that when these ants reach the nepenthes plant, its Peristome will be wet. So instead of finding food, they'll be the nepenthes' main course.