A Viscoelastic Deadly Fluid in Carnivorous Pitcher Plants

From Microcosm Aquarium Explorer

NepGrower/WikiCommons

Laurence Gaume1*, Yoel Forterre2*

Abstract

Background

The carnivorous plants of the genus Nepenthes, widely distributed in the Asian tropics, rely mostly on nutrients derived from arthropods trapped in their pitcher-shaped leaves and digested by their enzymatic fluid. The genus exhibits a great diversity of prey and pitcher forms and its mechanism of trapping has long intrigued scientists. The slippery inner surfaces of the pitchers, which can be waxy or highly wettable, have so far been considered as the key trapping devices. However, the occurrence of species lacking such epidermal specializations but still effective at trapping insects suggests the possible implication of other mechanisms.


Methodology/Principal Findings

Using a combination of insect bioassays, high-speed video and rheological measurements, we show that the digestive fluid of Nepenthes rafflesiana is highly viscoelastic and that this physical property is crucial for the retention of insects in its traps. Trapping efficiency is shown to remain strong even when the fluid is highly diluted by water, as long as the elastic relaxation time of the fluid is higher than the typical time scale of insect movements.


Conclusions/Significance

This finding challenges the common classification of Nepenthes pitchers as simple passive traps and is of great adaptive significance for these tropical plants, which are often submitted to high rainfalls and variations in fluid concentration. The viscoelastic trap constitutes a cryptic but potentially widespread adaptation of Nepenthes species and could be a homologous trait shared through common ancestry with the sundew (Drosera) flypaper plants. Such large production of a highly viscoelastic biopolymer fluid in permanent pools is nevertheless unique in the plant kingdom and suggests novel applications for pest control.


Read the full article on PlosOne.


1 CNRS UMR5120-AMAP, Montpellier, France, 2 IUSTI CNRS UMR 6595, Université de Provence, Technopole Château-Gombert, Marseille, France

Citation: Gaume L, Forterre Y (2007) A Viscoelastic Deadly Fluid in Carnivorous Pitcher Plants. PLoS ONE 2(11): e1185. doi:10.1371/journal.pone.0001185

Academic Editor: David Lynn, Emory University, United States of America

Received: July 21, 2007; Accepted: October 25, 2007; Published: November 21, 2007

Copyright: © 2007 Gaume, Forterre. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.