The pitcher plant Nepenthes alata, which inhabits the forests of Indonesia, has one of the most dramatic organs of any carnivorous plant, as the picture here attests. In this month's New Phytologist (156, 479–489; 2002), Laurence Gaume and colleagues describe their investigations of the features that make this vessel so efficient at trapping insects.
Gaume et al. tested the ability of N. alata to capture ants and a flightless strain of fruitfly. Victims were placed on the pitcher's ridged rim. Few escaped, because any insects that stepped onto the waxy zone covering half of the pitcher's inner surface almost inevitably fell to their doom. Ants managed to hang on to the waxy zone slightly longer than flies, and rather than fall straight into the pool of digestive fluid at the bottom of the pitcher, some landed on the layer of glandular cells that coat the bottom half of the pitcher wall. But the cells secrete a viscous substance that prevented these ants, or the few that managed to clamber out of the digestive pool, from escaping their fate as insect stew.
Electron-microscopic investigation of the surfaces provided clues to their properties. In the case of the waxy layer, the covering is flaky and so breaks off easily — explaining why flies, which can normally cling tenaciously to a smooth surface, fell from it faster than ants. But that cannot be the whole story, as ants still had difficulty climbing surfaces from which wax had been removed with chloroform.
This study illuminates how the cunning adaptations of N. alata's epidermal surfaces make the plant deadly to almost every insect that strays under its pitcher's lid. It might also inspire chemists to consider uses for materials with similarly exotic surface properties.
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Surridge, C. On the slide. Nature 420, 753 (2002). https://doi.org/10.1038/420753a